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Full text of "Lectiones Cutlerianae, or A collection of lectures, physical, mechanical, geographical & astronomical : made before the Royal Society on several occasions at Gresham Colledge [i.e. College] : to which are added divers miscellaneous discourses"

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LeSfiones Cutkriance, 

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LECTURES: 



(PHTSICAL, 

MECHANICAL, 

GEOGRAPHICAL, 
& 

ASTRONOMICAL. 



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Made before the Royal Society on feveral 
Occafions at Gresham Colledge. 

To which are added divers 

Miscellaneous Discourses. 



By ROBERT HOOKE, S.R.S. 



LONDON: 

Vnnte&fov John MartynVrmtextothzRoyalSocieiy, 
at the Bell in S. Pauls Church-yard. 1679. 



_ p 
SCV 1 & 



The Titles of the feveral TRACTS. 

L- AN ATTEMPT to prove the Annual MOTION of the EARTH 
JTJl by Obfervations made with accurate Inftruments : wherein is (hewn the 
Impofibiliiy of doing it, by the mofl exatt Inftruments and ways ufed by pre- 
ceding Aftronomers. The Inftruments and method ufed in theft Obfervati- 



ons: Ibe way of feeing the fixed Stars in the Day time ; and a new Hypo- 
thecs for folving the motions of the Heavenly Bodies U hinted. 
H. ANIMADVERSIONS mtheMzchim CcMis of Mr. Ucvc- 
lms, wherein is detected the imperfection of Aftronomkal Inftruments hitherto 
ufed, and divers ways of reforming and perfecting thofe and feveral other In- 
ftruments are explained and defcribed. And feveral other new Inventions are 
added and explained^ particularly Water-Levels ; The Circular Pendulum 
the Perfection of Wheel-wor\for Clocks and Watches, Sec. together with 
their ufes^ and the great advantage of thtfe above other Inventions of the like 
nature. • 

III. A DESCRIPTION of Heliofcopes with other liniments. 
Wherein are Difcovered and Defcribedy feveral new ways of making GlajTes 
tolookjtpon the Body of the Sun without offence to the Obfervers Eye. 2. A 

. jhortning Refle&ive and Refractive Telefcope. 3 . A way of ufmg a Glafs of 
any length without moving the Tube. 4. An Inftmmentfor taking the Di- 
ameter of the Sun, Moon and Planets*, or other fmall D iftanee sin the Heaven, 
to the certainty ef a Second. 5. An Inftrument for defcrib'mg all manner of 
Dials by tjje Tangent Projeclion. 6. The ufes of the faid iJiftrument, 
Firft,foradjuftingtheHandofa Clock^foMto mafy it move inthefhadow 
of a Dial, whofe Stile is parallel to the Axis i Or, Secondly, in the Azimuth 
of ' any Celeftial Body, that is, in the jhadow of an upright, or any other w&y 
inclining ftyle, upon any plain. Thirdly, for making a hand move according 
to the true JEquation ef Time. . Fourthly, for making all manner of Elliptical 
Dials, in Mr, Fofter's way, &c. Fifthly, for communicating a circular 
motion in a Curve Line, without any fhaking : And for divers other excel- 
lent purpofes. To which is added an Observation of the Eclipfe of the Moon, 
Tan, 1. 167$. And a Poftfcript concerning the Invention of regulating 
Watches, by Springs applyedto their Ballances : together with a Decade of 
ether ufeful Inventions, part difcovered, part defcribed in Anagrams. . 

W»>LAM->- 



The Titles of the feverai TRACTS. 

IV. LA MP AS, or Defections of fome Mechanical Improvements of Lamps 
and Water-poifes, with other Phyfcal and Mechanical Vifcoveries. Wherein 
are difcovered befides the ways of obviating the inconveniencies of other contri- 
vances of Lamps, Eight feverai ways of making Lamp fo, as to regulate the 
flame of them for various ufes : feverai of which are therein mentioned and' 
explained: Befides which, various ways and ufes are defcrihed ofpoyftng 

■ liquors, by the by, feverai theories and Explications are infertcd, particularly 
ahut Flame and Burning, about Light, Colour, Gravity, Local Motion, Pref- 
fure of Fluids, &c. in Anfiver to fome Objections of Dr. More, againfl 
fome former Vifcourfes publijhedby the Author, To thefe are added the 
Vefcription of a new fort of Clepfydra or Water-Clock* 2. A new Prin- 
ciple for regulating Pocket Watches. 3. Several Microfcopical Obfervations 
about the Seeds, of Mojfe, Mufhrooms, all h^nds of Ferns, Wall-Rue, Harts- 
Tongue^ Ofmund Royal, &c. 4. An Obfervation of $ots in the Sun. 

V, CO MET A, containing Obfervations on the Comet in April, 1677. 
Alfofortbeyears\664 r 1665. Sir Chriftopher Wren 5 / Hypothecs and 
Geometrical Problem about thofe Comets, A Vifcourfe concerning the 
Comet, 1677. 

Mr, BoylV Obfervation made on two new Phofphori of Mr, Baldwin, and 
Mr, Craft. 

Mr, GalletV Letter to Mr, Caffini, together with \m Obfervation of $ Cub 3. 

Mr, CaffiniV Reflections upon thofe 0/ Gaflendus and Hevelius, andupon this* 

Mr. Hally V Letter and Obfervation of the fame made at St, Helena. 

Mr, Caffinf / Obfervation of the Viurnal motion of # , and other Changes hap- 
pening in it, 

MICROS COP I UM, containing Mr, Leeuwenhoecks two Letter? 
concerning fome late Microfcopical Vifcoveries, 

The Author's Vifcourfe and Vefcription of Microfcopes, improved for difceming 
the nature and texture of Bodies, 

P. Ghembines Accufations Anfwered. 

Mr. YongeV Letter containing feverai Anatomical Obfervations. 

VL LECTURES dePotentiaRemtutivaoro/Spring,E^i^^e 
Power of Springing Bodies, To which are added fome Collections, viz. 

A Vefcription of Vr, Pappins Wind-Fountain and Force-Pump. 

Mr. YongV Obfervation concerning natural Fountains. ■ 

Some other Confederations concerning that Subjeft. 

Copt. SturnayV Remarks of a Subterraneous Cave and Cifiern. 

Mr.G. T. his Obfervations made on the Pike of TenerirT, Anno I 674. 

Some Reflections and Conjectures occafwned thereupon. 

A Relation of a late Eruption in the Ijle o/Palma. 



AN 

ATTEMPT 

To prove the 

MOTION 

O F T H E 

E A R T 

FROM 

Obfervations 

MADE BY 

ROBERT HOOKE Fellow of the 
Royal Society. 




Senec. Nat. Qu. lib. i . cap. 30. 
Ne miremur tarn tarde erui qua tam alte jacent. 



LONDON, 

Printed by T. R. for John Martyn Printer to the Royal Society ', 
at the Bell in St. Pauls Church -yard. 1674. 




TO THE 




KNIGHT and BARONET 




A. 











The Epflle Dedicatory. 
deferves to be R ecorded as One , and more 
efpecially by me whom you have honoured 
by eftabJifhing your firft Le&urer. As an 
Earneft of others more confiderable fliortly 
to follow, I Jhere prelent you with one of 
my Difcourfes in that Employment, which 
though fhort and plain , conteins fomewhat 
of Information which the Learned have hi- 
therto defired, though almoft with de/pair. 
As I hope their kind Acceptance will pro- 
duce their thanks to you to whom they are 
juftly due, fo your Acceptance will incou- 
rage me in the further profecution of thefe 
Inquiries to approve my felf, 



From Gnfh&m Colledgt, 
March 25. 1674. 



Noble Sir y 

Tour moft obliged, and 
w$l humble Servant 

Robert Hooke. 










JtjL % «j 

Have formerly in the Preface of my Micrographia 
given the World an account of the founding a Phy- 
fico-Mechanical LeQure in the Tear \66<$,by 
Sir John Cutler,/^ the promoting the Hiflory of Na- 
ture andofArtJnprofecution thereof J have cplldied many 
Obfervations both of the one and the other kind , and from 
time to time (at obliged) I have acquainted the R oyal 
Society at their PublicKMeetings, both tf*Gre(ham Col- 
ledge and Arundel Houfe therewith, by Difcourfes and 
Leftures thereupon. 

Now in order to the further promoting the End and De- 
fign of this Lefture, I have comply ed, with the defire of 
fever alof my friends (though otherwife not thereunto obli- 
ged) to commit divers ofthofe Difcourfes to the PiMck., 
though of themfelves for the moSlpartincompleat, andEC- 
fayes or Attempts only upon fever al Sub)e&$ which have 
no dependencie or coherencie one with another* In the do- 
ing hereof, Idefign to avoid any kind of Method or Order 
that may require Apologies, Prefaces, or needlefl Repetitions 
of what i* already known, or might have been faid upon that 
Occafion, or may neceffitate metofolhw thUor thatSubjefi, 
that doth n$t fome way or other offer it felf at it were, and 

prompt 



To the Reader, 

prompt me to the moderation thereof But becaufe they 
maypofibly admit of fome better order hereafter , I defign 
to print them all of the fame Volume, that fo they may be, 
when ranged \ either flit ched or bound together, and may % m 
occafion requires, be referred to undtrthe Title of their Num- 
ber and Page, Thh way Ichufe fs the beSl for promoting 
the Defign of thh Lefture;^ at there hfcarce one Subject 
of millions that may be pitched upon, but to write an exaft 
andcompkat Hiflory thereof, would require the whole time 
and attention of a mam life , and fome thoufands of Inven- 
tions and Obfervations to accomplish it: So on the other fide 
no man h able to fay that he will compkat thh or that In* 
q&iry, whatever it be, (The greatest part of Invention be- 
ing but a luckey hitt of chance, for the 'moSi part not in our 
own power , and like the wind, the Spirit of Invention blow- 
eth where and when it lifteth, and wefcarce know whence 
it came, or whether 'tis gone.) 'Twill be much better there- 
fore to imbrace the influences of Providence, and to be dili- 
gent in the inquiry of every thing we meet with. For we 
pall quickly find that the number ofconfiderable Obferva- 
tions and Inventions thh way toileted, will a hundredfold 
ouuflrip thofe that are found by Befign. No man but hath 
fome luckgy him and ufeful thoughts on thh or that $ubje£$ 
he U converfant about, the regarding and communicating of 
which wight be $ means to other Perfons highly to improve 
them. Whence 'twere, much to be wifkd 1 that others would 
takf thh Method in ' their ; Puhlicntions, and not torment 
their Readers withfuch nmfeomtepttiilons^nd 'frivolom 

Apologies, 



To the fleader. 

Apologies, 06 Method and Volumes do neceffitate them to ; But 
would rather Inrich theStore-houfe of Art and Nature wkh 
choice and excellentSeed,freed from theChaff andDrofs that 
do othermfe bury and corrupt it , 

The communicating fuch happjThoughts and Occurrence* 
need not much take up a mam time to fit it for the Pre/1 ; 
the Relation being fo much the better the plainer it k. And 
matter of Fatt being the Kernel Readers generally defire(at 
leaft in thefe Subjects) it will be fo much the readier for ufe 
if it be freed from the thick, and hard f ffjell of Impertinences. 
Thi* way alfo it more grateful both to the Writer and the 
Reader, who proceed with a frefh ftomach upon variety, 
but would be weary and dulld if neaffitatcd to dwell too 
long upon one Subject. There are ether conveniencus alfo 
in this Method of Communication not lefl confiderable then 
the former, among ft the reft the fecuring of Inventions to 
their fir il Authors, which Yps hardly poffible to do by any c- 
ther means; for there are a fort of Per fom that make it their 
bufmefl to pump and fly out others Inventions, that they may 
vend them to Traders of that kind, who thinkjthey do wge- 
nuoufly to print them for thar own, fince they- have bought 
and paid for them. Of this there have lately been fomeln- 
dances, and more may be expefled, if this way prevent not. 

When things cannot be well explained by words* only 
(which k frequent in Mathematical ^Mechanical Dill 
courfes) / adde Schemes and delineation* Defcriptlons of 
that kind being eafur to be made and underfiood. As. 
near as I can I omit the repeating things already printed, 






To the Reader. 
arid indeavour to deliver fuch m are new anh my tmnjteing 
my felfbtftpltafed with fuch ufagefrom ether Authors. 

I have begun with a Difcourfe compofed and read in 
Grefham Golledge in the Tear 1670. when Idefignedto 
> have printed it, but wot diverted by the advice of feme 
Friends to ftaj the repeating the Obfervation> rather then 
publifk it upon the Experience of one Tear only. But finding 
that Sicknefs hath hitherto hindered me from repeating the 
Try ah, and that fome Tears Obfervations have already been 
loft by the fir ft delay : I do rather haft it out now, though 
imperfttt, then detain it for a better compleating, hoping it 
may be at kaft a Hint to others to profecute and compkat 
the Obftrvathn, which I much long for. 

Thhfirft Difcourfe hjtponan Obfervation jtf Nature , 
and may therefore be properly refer red to that Head , though 
it contein alfo fomewhat of the Improvement of Art: The, 
fecond fteedily to follow / will more properly be referrableto 
Artificial improvements , though it will contein alfo ma- 
ny Obfervations of Nature ; and I defign alwayes to make 
them follow each other by turns, and as 'twere to interweave 
them, bang apart but like the Warp or Woof before contex- 
ture, unfit either to Cloth, or adorn the Body of Philo- 
fophy; 



AN 



CO 



Kttm!>. x » 




A N 

ATTEMPT 

To prove the Motion of the 

EARTH 

BY 

OBSERVATIONS. 

>Hether the Earth move or flandftill hath 
beenaProb'em, that fince Copernicm revi- 
ved it, hath much exercifed the Wits of our 
beft modern Aftronomers and Pbiiofophers, 
amongft which notwithstanding there hath 
not been any one who hath found out a cer- 
tain manifestation either of the one or the 
• j- • u r oth erDoarine. The more knowing and 
judicious have for many plaufible reafons adhered to the Coperni- 
roHypochefis: But the generality of others, either out of ig- 
norance or prejudice, haverejefleditas a moft extravagant o~ 
pinion. To thofe indeed who underftand not the grounds and 
principles of Aftronomy, the prejudice of common converfc 

B doth 




(2) 

doth make it feem foabfurd, that a man fhall asfoon perfwade 
them that the Sun doth not fhine, as that it doth not move ; and 
as eafily move the Earth as make them believe that it do's To al- 
ready. For fuch Perfons I cannot fuppofe that they ihould under- 
ftand the cogency of the Reafons here prefented , drawn from 
the following observations of Taraltax, much IeiV< thereto recan 
Iexpefl; their belief and affentthereuntajtb them I have only this 
to fay, Tis not here my bufinefs to inftruci them in the firft prin- 
ciples of Agronomy, there being already Introductions eno/gh 
for that purpofe : But rather to furnifh the Learned with an e x- 
ferimentum cruris to determine between xheTychonick and Coper ni- 
can Hypothefes. That which hath hitherto continued the difpute 
hath been the plaufiblenefs of fome Arguments alledged by the 
one and the other party, with fuch who have been by nature 
or education prejudiced to this or that way. For to one that 
hath been converfant only with illiterate perfons, or fuch as 
underftand not the principles of Aftronomy and Geometry, and 
have had no true notion of the vaflnefs of the Qniverfe^and the ex- 
ceeding mi nutenefs dftheGlobe of the Earth in companion there- 
with, who have confined their imaginations & fancies only with- 
in the compafs and pale of their own walk and profpedt,who can 
fcarce imagine that the Earth is globous, but rather like fome 
of old, imagine it to be a round plain covered with the Sky as 
withaHemifphere, and the Sun, Moon, and Stars to be holes 
through it by which the Light of Heaven comes down ; that 
iuppofe themfelves in the center of this plain , and that the Sky 
doth touch that plain round the edges, fupportedinpartby the 
Mountains ; that fuppofe the Sun as big as a Sieve^ndrthe Mqqd 
as a Cheader Cheefe, and hardly a mile off. That wonder wliy 
the Sun,Moon,and Stars do not fall down like Hail-frbnes 5 arid 
that will be martyr'd rather then grant that there may be Afiti- 
podes,believiogitabfolutely impoffible,fince they muft neceFa- 
rily fall down into the Abyft below them: For how can they go 
with their feet towards ours,and their heads downwards,with- 
out making their brains addle. To one I fay,thus prejudiced with 
thefeanda thoufand other fancies and opinions more ridiculous 
and ab'furd to knowing men, who can ever imagine that the uni- 
formity and harmony of the Geleftial bodies and motions,flhould 
be an Argument prevalent to perfwade that the Earth moves a- 
b'outtheSun: Whereas that Hypothefis which thews-how to 

falve 



(3) 

falve the appearances by the reft of the Earth and the motion of 
the Heavens, feems generally fo plaufible that none of thefe can 

refill it. 

Now though it may belaid, 'Tis not only thofe but great 

Geometrician?, Aftronomers and Philofophers have alfo adhe- 
red to that fide, yet generally the reafon is the very fame. For 
moft of thofe, when young, have been imbued with principles 
asgrofsand rude as thofe of the Vulgar, efpecially as to the 
frame and fabrick of the World, which leave fo deep an im-* 
predion upon the fancy, that they are not without great pain and 
trouble obliterated: Others, as a further confirmation in their 
childifli opinion, have been inftructed in the Ptolomaick or Ti- 
cbonick Syftem,and by the Authority of their Tutors, over-awed 
into a belief, if not a veneration thereof : Whence for the moft 
part fuch perfons will not indure to hear Arguments againft it, 
and if they do, 'tis only to find Anfwers to confute them. 

On the other fide, fome out of a contraditfing nature to their 
Tutors 3 others,by as great a prejudice of inftitution ; and fome 
few others upon better reafoned grounds, from the proportion 
and harmony of the World, cannot but unbrace the Cofernican 
Arguments, asdeuionftrations that the Earth moves, and that 
the Sun and Stars ftand ftill. 

I confefs there is fomewhat of reafon on both fides, but there 
is alfo fomething of prejudice even on that fide that feems the 
mofir rational. For by way of obje6ion% what way of de- 
monstration have we that the frame and conftitution of the 
World is fo harmonious according to our notion of its harmo- 
ny, as we fuppofe f Is there not a pofiibility that the things may 
beotherwife ? nay, is there not fomethingof probability .<? may 
not the Sun move as Ttcho fuppofes, and the Planets make their 
Revolutions about it whilft the Earth Hands ftill, and by its 
niagnetifmattra&stheSun, and fo keeps him moving about ir, 
whilft at the fame time $ and 2 move about the Sun, after the 
fame manner as ft and V move about the Sun whilft the Satellites 
move about them *? efpecially fince it is not demonftrated with- 
out much art and difficulty, and taking many things for granted 
which are hard to be proved, that there is any body in the XI- 
niverfe more considerable then the Earth we tread on. Is there 
not much reafon for the Hypothefis of licho at leaft, when he 
with all the accuratenefs that he arrived to with his vaft Tnftru- 

B 2 ments 



w 

mients,or Riccioti, who pretends much to out-ftrip him, were 
not able to find any fenfible Parallax of the Earths Orb among 
the fixt Stars, especially if the obfervations upon which they 
ground their after tions , were made to the accuratenefs of fome 
few Seconds/ What then, though we have a Chimera or Idea 
of perfection and harmony in that Hypothefis we pitch upon , 
may there not be a much greater harmony and proportion in the 
conftitution it fe]£ which we know not, though it be quite 
differing from what we fancy i Probable Arguments might thus 
bavebeen,urged both on the one and the other fide to the Worlds 
end ; but there never was nor could have been any determina- 
tion of the Controverfie, without fome poficive obfervation for 
determining whether there were a Parallax or no of the Orb of 
the Earth ; This ticbo and Rmkli affirm in the Negative, that 
there is none at all ; But I do affirm there is no one that can either 
prove that there is, or that there is not any Parallax of that Orb 
amongftthe fixt Stars from the Suppellex of obfervations yet 
made either by luho % Ricckli, or any other Writer that I have 
yet met with from the beginning of wTiting to this day* For 
all Obfervators having hitherto made ufe of the naked eye for 
determining the exaft place of the ob;e&, and the eye being un- 
able to diftinguifh any angle lefs then a minute, and an obfer- 
vation requifite to determine this requiring a much greater ex- 
aftnefs then to a minute, it doth neceffarily follow that this 
fxftrimentum cructi was not in their power, whatever either 
Tufa or Riccieli have faid to the contrary, and would thence 
overthrow the Copernican Syftem, and eftablifh their own* We 
are not therefore wholly to acquiefs in their determination, 
fince if we examine more nicely into the obfervations made 
by them, together with their Jnfrruments and wayes of ufing 
them, we ihall find that their performances thereby were far? 
otherwife then what they would feem to make us believe. The 
Gontroverfie therefore notwithftanding all that hath been faid 
either by the one or by the other Party, remains yet undeter- 
mined, Whether the Earth move above the Sun, or the Sun about 
the Earth > and all the Arguments alledged either on this or that 
fide,, are but probabilities at befiy and admit not of a necefla- 
ry and pofitive conclufion. Nor is there indeed any other 
means left for humane induftry to determine ir, fave this one 
which I have endeavoured to make 5 and the unquestionable 

certainty 



C5) 

certainty thereof is a moft undenyable Argument of the truth of 
the Cepemcan Syfteme ; and the want thereof hath been the 
principal Argument that hath hitherto fomewhat detained me 
fromdeclaringabfolutely for that Hypothefis, for though it 
doth in every particular almoft feem to folve the appearances 
morenaturally and eafily , and to afford an exceeding harmoni- 
ous constitution of the great bodies of the World compared 
one with another , as to their magnitudes, motions, and di- 
fiances, yet this objection was alwayes very plaufible to moft 
men, that it is affirmed by fuch as have written more particular- 
ly of this fubjeft, that there never was any ferifible Parallax dif- 
covered by the beft obfervations of this fuppofed annual mo- 
tion of the Earth about the Sun as its center, though moved m 
an Orb whofe Diameter is by the greateft number of Aftrono- , 
mers reckoned between n and 12 hundred Diameters of the 
Earth : Though fome others make it between 3 and 4 thoufand ; 
others between 7 and 8 . and others between 14 and 15 thou- 
fands ; and I am apt to believe it may be yet much more , each 
Diameter of the Earth being fuppofed to be between 7 and 8 
thoufand Englifh miles, and confequently the whole being re- 
duced into miles, if we reckon with the moft, amounting to 1 20 - 
millions of Englift miles, ft cannot, I confefs, but feem ve- 
ry uncouth and ftrange to fuch as have beenufed to confine the 
World withlefsdimenfions, that this annual Orb of the Earth 
of fo vaft a magnitude,fhould have no fenfible Parallax amongft 
the fixt Stars, and therefore 'twas in vain to indeavour to an- 
fwer that objection. For it is unreafonable to expea that the 
fancies of moft rnenftouldbefofarftreined beyond their nar- 
row dimenfions, as to make them believe the extent of the Uni- 
verfe To immenfly great as they muft have granted it to be fu p. . 
pofing no Parallax could have been found. * 

Thelnquifitivejefuit Riechli has taken great pains by 77 
Arguments to overthrow the Cepernican Hypothefis, and is 
therein foearneft and zealous, that though otherwife a very 
learned man and good Aftronomer, he feems to believe his own 
Arguments; but all his other 76 Arguments might have been 
fparedas to moft men, if upon making obfervations as; I have 
done, hecoufd have proved there had been no fenfible Paral- 
lax this way difcoverable, as I believe this one Difcovery will 
anfwer them, and 77*aore, if fo many can bt thought of and 

produced 



(6) 

produced againft .it. Though yet I confefs had I fail'd in difa^ 
veringa Parallax this way, as tomyown thoughts and perfwa- 
fion, the almoft infinite extenfion of the Univerfe had not tome 
feem'd altogether fo great an abfurdity to be believed 3s the 
Generality do efteem it 5 for fince 'tis confeffedly . granted pn all 
hands the diftance of thefixt Stars is meerly hypothetical, and 
not founded on any other ground or reafon but fancy andfuppo* 
fition, and that there never was hitherto any Parallax obferved, 
nor any other confiderable Argument to prove the diftances fup- 
pofed by fach as have been mod curious and inquifitive in that 
particular,! fee no Argument drawn from the nature of the thing 
that can have any neceffary force in it to determine that thefaid 
. diftance cannot be more then this or that , whatever it be that is 
atfigned. For the fame God that did make this World that we 
would thus limit and bound, could as eafily make it millions of 
millions of times bigger, as of that quantity we imagine ; ancj 
all the other appearances except this of Parallax would be th.e 
very fame that now they are. To me indeed the Univerfe feems 
to be vaftly, bigger then 'tis hitherto aiTerted by any Writer , 
when I confider the many differing magnitudes of the fixt Stars, 
and the continual increafe of their number according as they 
Jt * M^-^ are looked after with fetter and longer Telefcopes. And could 
C'^!n?^ v '/ vv ^ certainly determine and meafure their Diameters f and di- 
[21 . ^ 0uiL h ^%inguifh what part of their appearing magnitude were to be at- 
^h 'fakfyi- tributed ro their bulk, and what to their brightnefs, Iamapt 
to believe we fhould make .another diftribution of their magni- 
tudes, then what is already made by Vtolomy , %tcho, 
Kepler, Bayer, Clavm, Grknbergem, Fiff, Hevelws ando- 

For fiippofing all the fixt Stars as fo many 3u^s,, -and 
( each of them to have a Sphere of afiivity or expanfion pro- 
\ portionate to their folidity and aftivity , and a bigger and 
\ brighter bodied Star to ijave a proportionate bigger fpace 
\ or expanfion belonging to it , we flipuld from the knowledge. 
I of their Diameters and brightnelTes be better able to ;udge 
of their diilances, and confcquently afiign divers of them 
other magnitudes then thofe already ftated : Efpecialiy fince 
we now find -by- .observations., that of thofe which are ac- 
counted (ingle Stars , divers prove a congeries of many Stars, 
\ though from their near appearing to ea»ch other , the na- : 



Y7) 
ked eye cannot diftinguifli them; Such as thofe Stars which 
are called Nebulous, and thofe in Orion Sword, and that in 
the head of Aries , and a multitude of others the Telefcope 
doth now detect* And poffibly we may find that thofe 
twenty magnitudes of Stars now difcovered by a fifteen 
foot'Glafs, may be found to in create' the magnitude of the 
Semidiameter of the vifible World, fourty times bigger then 
the Gopernicans now fuppofe it between the Sun and the 
fixt Stars, and confequently fixty four thousand times ia 
bulk. And if a- Telefcope of double or treb'e the good- 
nefs of one of fifieeniliould- dif cover double or treble the 
faid number of magnitudes, wbuld it not be an Argument 
of doubling or trebling^ '-the former Diameter, and of in- 
creafing the bulk eight or twenty feven times* Efpeciai !y if 
jheir apparent Diameters fhall be found reciprocal to their Di- 
fiances (for the determination of which I did make fomeob^ 
fervations; and defign to compleat with what ^ptGd T am able.) 
But to.digrefs no further, This grand objection df the Ami- 
copernicans, which to mod men feem'd fo plaufible, that it was 
in vain tooppofeit, though, I fay, it kept me from declaring 
abfolutely for the Cofemicm Hypothefis, yet I never found any 
abfurdity or impoffibility that followed thereupon: And I 
alwayes fufpeded that though fome great Aftronqmers had af- 
ferted that there was no Parallax to be found by their obfervati- 
ons, though made with great accuratenefs, there might yet be 
a pofllbility that they might be miftaken^ which made me a!- 
wayes look upon it as an inquiry well worth examining: firfr 9 
Whether the wayes they had already attempted were not fubjccl 
andlyable to great errors and uncertainties: and fecondly , 
Whether there might not be Tome other wayes found out which 
fliould be free from all the exceptions the former were incum- 
bred with, and be fo far advanced beyond the former in cer- 
tainty and accuratenefs, as that from the diligent and curious 
ufe thereof, not only all the objections againft the former might 
be removed, butt all other whatfoever that were material to 
prove t he dnerTe&ualnefs thereof for 1 this purpofe. : 

Jbegan therefore firfho examine intothe matter as it had al- 
ready been performed by thofe who had afTerted iio fen fible Pa- 
rallax Of the annual Orb of the Earth, and quickly found that 
(whatever they aflerted) they could never determine whether 

there 



there were any or no Parallax of this annual Orb; especially if ' 
it were lefs then a minute, which Kef ler and Riccioli hypotheti- 
cally affirm it to be: The former making it about twenty four 
Seconds, and the latter about ten. For though ttcfo f a man 
of unqueftionable truth in his afTercions , affirm it poffible to 
obferve with large Inftruments, conveniently mounted and fur- 
nifhed with fights contrived by himfelf ( and now the common 
ones for Aftronomical Inftruments; to the accuratenefs of ten 
Seconds ; and though Riccioli and his ingenious and accurate 
Companion GrmaUizfarm it poffible to make obfervations by 
their way, with the naked edge to the accuratenefs of five Se- 
conds ; Yet Kefler did affirm, and that jjuftly, that 'twas im- 
poflible to be fure to a lefs Angle then 12 Seconds; And I 
from my own experience do find it exceeding difficult by any 
of the common fights yet ufed to be fure to a minute. I quickly 
concluded therefore that all their endeavours muft have hitherto 
beenineffe&ualtothispurpofe, and that they had not been lef* 
impofed on themfelves, then they had deceived others by their 
mifraken obfervations. And this raiftake I found proceeded 
•from divers inconveniencies their wayes of obfervations were 
lyable to. As firft from the fliriuking and ftretching of the mate- 
rials wherewith their Inftruments were made, I conceive a much 
greater angle then that of a minute may be mifraken in taking an 
.altitude of fifty Degrees. For if the Instruments be made of 
Wood, 'tis manifeft that moyft weather will make the frame 
ftretch, and dry weather will make it fhrink a much greater 
quantity then to vary a minute: and if it be Metal , unlefsitbe 
provi4ed for in the fabrick of the Inftrument accordingly, the 
heat of Summer , when the Summer obfervations are to be made 
will make the Quadrant fwelj, and the cold of Winter will make 
it fhrink much more then to vary a minute; Both which incon- 
veniencies ought to be removed. Next the bending and warp- 
ing of an Inftrument by its own weight, will make a very con- 
fiderable alteration* And thirdly, the common way of Divifi* 
on is aifo lyable to many inconveniencies : And 'tis hardly pof- 
fible to afcertaiq all the fubdivifions of Degrees into minutes 
for the whole Quadrant, though that be not altogether impof- 
fible. But I will fuppofe that they did forefee, and in fome 
manner prevent all thefe inconveniencies, efpecially Tieho and 
Riccioli, who feem to have been aware thereof. But there was 

one 



C9) 

one inconvenience which was worfe then all the reft, which 
they feem not to have been Efficiently fenfible of, from whence 
proceeded all their own miftakes, and their hnpofing upon o- . 
thers and that was from their opinion that the fight of the 
naked eye was able to diftinguifli the parts of the 
object as minutely as the limb of the Quadrant (of what 
argenefsfjever; was capable of Divifiors ; w hereas 'tis hard- 
ly poffible for any unarmed eye well to diftinguiih any Angle 
much fmaller then that of a minute : and where two objefls are 
not farther diftant then a minute, if they are bright objefis, 
they era ..eft and appear one , though I confefs , if they be 
dark ob;ecb, an d a light be interpofed, the diflance between 
them fhall be vifible, though really much left then a Second ; 
and yet notwithftanding, my firft affcrtion ftands good; for 
though a bnght objects a candle or light ata diftance.oraStar, 
or the like,can be leen by the eye, though its body do really not 
Hbtend an Angle of one third , yet it proceeds from a radiation 
(that is,from reflection and refraction together) in the air and in 
the eye,whereby the body thereof is reprefented to the naked 
eye fome hundred times bigger then it really is. That this is 
i.\ any one that will but carefully examine will find it true. 

It was, I doubt not, their extraordinary defire and care to 
be exact, that caufed them to make their Instruments fo large, 
andtofubdrvidethemtofuchanexaflnefs, as to diftinguiih, 
it poffible, to Seconds ; And I queftion not but that they ufed 
tberrutmoft indeavourindiredingthe fight to the object: but 
Jince the naked eye cannot diftinguifli an Angle much fmaller then 
a minute, and very few to a whole minute, all their charge and 
trouble in making and managing large Inftruments, and in cal- 
cu'aungand deducing from them, was as to this ufe in vain, 
hence lodged that whatever mens eyes were in the younger 
age of the World, our eyes in this old age of lt needed Specta- 
cles ; and therefore I refolved to aflift my eyes with a very 
arge and good Telefcope, inftead of the common fights, where- 
by I can with eafediftingaifli the parts ofan object to Seconds: 
and I queftion not but that this way may be yet made capable of 
difhnguifhmg much more curioufly, poffibly even to fome few 

i'T'iir T ention removed that grand inconvenience 
which all former obfervations were fpoiled with : but there re- 

C ; mained 



mained yet further this difficulty, How ta make ait Infteument 
large enough for this purpofe, that I might be affured did not 
fib rink, nor warp, norftretch fo much as to vary a Second } 
4 for fuch is the nature of all Materials that can be made d{q of 
for Instruments of the bignefs I defigned this , that 'tis almoft 
itnpofpble to make a moveable Internment that fball not be 
fubjed to a variation of divers Seconds ;.. It was therefore my 
next inquiry where I might fix this Archimedean Engine thac 
was to move the Earth, For the doing of which, I knew 'twas 
in vain to confuk with any Writer or Afhonomer, having never 
then heard of any perfon that had ever before that time had any 
thoughts thereof:- and when I fkft propounded it to the Royal 
Society, 'twas look'd upon as a new thought, and fomewhat 
extravagant, and hardly pradi cable.,, until upon hearing my 
explication, and the various wayes how it might be reduced 
intopradife, it was at length judged poffible, and -deferable - 
to be tryed. I propounded therefore to them the feveral ways 
that it was poflible to be performed , and.what method was to 
be obferved in every one of them , and fomewhat of the con- 
veniencies and inconveniencies in each of them; for having fe-- 
rioufly meditated upon the Inquiry, I quickly thought of many 
expedients for the doing thereof. As finV I had thoughts of 
making u r e of fome very great and raaffy Tower or Wall that 
were well fetled, or of fome large Rock or Hill whereunto I 
might fix my Glaffes, €o as to take the exad altitude of fome e- 
minent Star near the Pole of the Ecliptik, .when at its greateft 
height, at two differing times -of the year ; to wit, about the 
Summer and Winter Solftice, to fee if poflibly I could difcover 
any difference of alticude between the fir ft and fecond obfer- 
vation. But toaccompiiOi this (betides the vaft difficulty 
there would have been to have meafured fuch an Angle to the: 
accuratenefs requifite, if at leaft it were-defired to have the 
Angle of altitude to Minutes and Seconds, which ought alfo to 
have been repeated as oft as any obfervation had been made for 
fear of fetling or fuelling, &c.) I wasdeftitute of fuch a con*- ' 
venience near my habitation; befides, had I had my wifii, I 
found that 'twas lyable to an inconvenience that would wholly 
overthrow my whole deCign, which I knew not well how to a- 
void: Namely, to that which hath hitherto made even the very 

beft 



<*0 

'heft obfervatrorts ©f Parallaxes ineffectual and uncertain , the 
refrattion of the Air or Jtmoffbere, which though it could 
tiave been but very little at the greateit altitude of the Pole of 
the Ecliptick, yet it might have been enough plauflbly to have 
fpoiled the whole obfervation , and to have given the Jnti- 
cofermcdm an opportunity of evading the Arguments taken 
from it , efpecially upon the account of the differing conftitu- 
t ion of the Atmofphere in June and December , which might 
have can fed fo much a greater refradion of the fame altitude at 
one time then another, as would have been fufikient to have 
made this obfervation ineffectual for what it was defigned. 
Addeto this , that it would have been no eafie matter to have 
fet the Glaffes or Tekfcope exaclly againft the Meridian, fo as 
to fee the big-heft altitude of any Star near the Pole of the Eclip- 
tick diitin&iy to a Second. 

The like difficulties I found if obfervations were made of the 
greateft altitude of the Pole of the Ecliptick in June and De- 
cember, or the leaft altitude of the fame in December -and June* 
For befides all the uncertainties that the Inftruments, be they 
what they will, are liable to, the grand inconvenience of the 
refraction of the Air, which is enough to fpoil all obfervations 
if it be intermixed with uncertainty, in the former is confidera- 
ble, and in the later intolerable. 

Having therefore examined the wayes and Inflruments for all 
manner of Agronomical obfervations hitherto made ufe of, and 
confidered of the inconveniencies and imperfeclions of them \ 
and having alfo duly weighed the great accuratenefs and cer- 
tainty that this obfervation neceffariJy required; 1 did next 
contrive a way of making obfervations that might be free frcm 
all the former inconveniencies and exceptions , and as near as 
might be , fortified againft any other that could be invented or 
raifed againft it. This way then was to obferve by the patting 
of fjme considerable Star near the Zenith of Grefi am Coll edge, 
whether it did not at one time of the year pafs nearer to it, and 
at another further from it : for if the Earth did move in an Orb 
about the Sun, and that this Orb had any fenfible Parallax a- 
mongft the fixt Stars 5 this muff neceffarily happen, efpecially 
to thofe fixe Stars which were neareft the Pole of the Eclip- 
tick. And that this is fo, any one may plainly perceive if he 

C 2 confide? 



m 

confider the annexed Scheme, Fig. I. where let S rcprefcnt the 
Sun placed as it were in the center of the Planetary Orbs, A- BCD 
an imaginary Orb of the fixt Stars of the firft magnitude, whofe 
center for demonftration fake we will fuppofe the Sim. Let 
r sr ^ reprefent theOrb in which tfcEarth is f ppofed to move 
about the Sua, obliquely proje&ed on the Paper. Let^re- 
prefent the Earth in Capricorn, and ® the Earth in Cancer, 
let i 2. i 2. reprefent the imaginary Axis of the Earth, keeping 
continually a parallelifin to its felf,and let V AECD © reprefent 
an imaginary Plain palling through the center of the Star at D 
in the SolfHtial Colure , and the two centers of the Earth in 
V> and © , and C reprefent the Zenith point of Grejham Col- 
ledge at noon, when the Earth is in Cancer , and A the Ze- 
nith pDint of the faid Colledge at midnight in the aforefaid Orb 
A BCD when the Earth is in Capricorn, 'tis manifeft there- 
fore that fince the Poles of the Earth, the Poles of the Eclip- 
tick , and the Zenith points of the Earth at noon , when in 
Cancer , and at midnight, when in Capricorn, are all in the 
fame Plain; and that the Axis of the Earth keeps a! way es its 
parallelifm , and that the Angles made by the Perpendiculars 
of Greftam Colledge, with the Axes are alwayes the fame, 
that the aforefaid Perpendiculars of the faid Colledge fhall be 
parallel alfo one to another , and confequently deno:e out two 
points in the abovefaid Orb A and C as far diftant from each 
other as the parallel Lines A^ and C© are, and confequently 
the point A fhall be farther from the Star in D, and the point 
C fliall be nearer to it, when in the Meridian near the Zenith 
of London , and confequently if the faid Star be obferved 
when in the Meridian of the place abovefaid ,. if there beany 
fuch difference confiderabte , it may be found if convenient 
Instruments and care be made ufe of for the obfervation there- 
of: and the difference between the Angle A'vicD, and the An- 
gle C^D, will give the parallactical Angle ^D^of the Orb 
of the Earth to the fixt Srar D of the firft magnitude. The 
fame demonftration will hold mutatis mutandis , fuppofing the 
Star be not in the Meridian or Plain abovefaid, but in 'feme 
other Meridian, as any one upon well confidering the nature 
of the thing it felf may eafily prove, if the obfervation be 
made when the Zenith pafTes by the Star at midnight, and at 

mid- 



03) 
mid-day* But the nearer the Zenith of the place of ofcferva* 
tion pafTeth to the Pole point of the Eciiptick, the better; 
The Angle of Parallax being ftill the more fenfible. There- 
fore the beft p!ace to compleat this obfervation were in fome 
place under the Polar Circles, as in//fW, where the Ze- 
nith of the p'ace at the times abovefaid , muit confequently 
pafs atone time to the North fide of the Pole of the Eciiptick, 
and at the other on the South fide, and the Zenith of March and 
Sept. muft pafs through the very Pole-point it felf. Now it 
falling out fo, that there is no confiderable Srar in that part 
of the Heavens nearer the above faid Plain, and nearer the Ze- 
nith point of Grefham folkdge in that Plain , then the Bright 
Star in the head of the Dragon, I made choice of that Star for 
the obje&by which I defigned to make this obfervation, find- 
ingthe Zenith point of Grefham Colledgeto pafs within fome 
very few minutes of the Star it felf; the declination thereof 
according to Riccioli being 5 1 °. 36'. 7". and the Plain the Star 
and Pole of the World,making an Angle with the aforefaid Plain 
but of 2 8 . 52. 36, the right afeention thereof being accord- 
ing to Ric&ioli 267 % 7'. 24'V 

And that this may be made a little plainer, let us fuppofe 
in the third Figure, the North part of the Heavens projected 
ftereographical upon a Plain to which the Axis is perpendicu- 
lar. Let p reprefent the Pole, e the Pole of the Eciiptick, 1 
the bright Star in the head of Draco , and let accc reprefent 
an imaginary Circle defcribed by the Zenith pi Grefbam Col- 
ledge among the fixt Stars in June , and b d d d a like Circle 
defcribed by the faid Zenith in December, and efff a like 
Circle defcribed as above in March, and g h h h in September* 
It is very evident that the true diftances of the Zeniths in that 
part of the Meridian which isnext thePoleof the Ecliptick,to 
wit,in the head of the Conftellation Draco jhd\\ be to the true di- 
ftances of the faid Zeniths in that part which is furtheft from 
the faid Po'e, to wit, near the conitellation of jtwiga in conj'e- 
quentia, as the fign of 73 degrees to the fign of 14 . 54', and 
the variation of the Zeniths, or the Angle of Parallax here at 
Grefoam Colledge, to the Angle of Parallax mlfeland, or any 
other place under the Pole of the Eciiptick, or Artick Circle 
is, as the fign of feventy five to the fign of ninety or the Radi- 






M. This will be very evident if we confider in' the fecond 
Scheme; AB to represent the Diameter of the great Orb; AC 
and BD the perpendiculars otlfeland , or fome other place 
under the Polar Circle. GA, HB the perpendiculars of Gre/ham 
Colledge in Draco: and LA, MB^the perpendiculars of the fame 
place to the Solftitial Golure near Auriga, the feveral di- 
ftances CD, GH, IK, LM, will be as the flgns of ?o°|7 5* 1 66°^o*| 
i4*.$4' I . to wit, as the Lines or Cords A B. AO. P B.QJ3. 

f might have made obfervations of thediftances of the tran- 
fitsof our Zenith from any other Star as well as from this of 
Draco , and the fame Phenomena might have been obferved , ta- 
king care to make one of the obfervations when the Star is ia 
the Zenith at midnight, and the other when the fame Star is in 
the Zenith at noon or mid-day } and upon this account when I 
next obferve, I defign to obferve the tranfits of our Zenith by 
Beneruim, mttenltimACMdAurfamajoris, it being a Star of 
the fecond magnitude, and having almoft. as much declinatiori 
as Grejham Colledge hath latitude. The principal dayes of do- 
ing which will be about the 4 of Jfrtl, when our Zenith paf- 
feth by the faidStar at midnight , and the 7 of Offober, when 
ft pafTeth by it at noon or mid-day: the reafon of all which 
will be fufficiently manifed to any one that iliall well confider 
the preceeding explanation. 

This Star I would the rather obferve, becaufeasit is pla- 
ced fo as that the Parallax thereof will be almoft as great as 
of the Po 1 ^ of the Ecliptick in Ifiknd , or under the Artick 
Circle, fo it being a Star of the fecond magnitude, and con- 
fequently perhaps as near again as one of the fourth, the An- 
gle of Pa/allax will be near about twice as big, and the Star ic 
felf much more ealie to be feen in the day time. This will be 
very eaiie to be understood , if we confider in the firft Scheme 
theditTenngdiftances of the Orb J B C D, in which we may 
fuppofe the Stars of the fecond magnitude to be fixt, and of 
the Orb *#*«a, in which we may fuppofe the Stars of the fourth 
magnitude, and abed in which we may fuppofe thofeofthe 
third magnitude^ and A B C Din which we may fuppofe thofe 
of the firft \ for if the Stars are further and further removed 
from the Sun, according as they appear lefs andlefs to us, the 
paralla&ical difference found by obfervatkm mule neceffarily 

be 



(if) >• 

be lefs and "lefs, according as- the obfer ration is made of left 

and lefs Stars. • 

The reafons then why.1 made choice of this way of obferving 
wiH be eafie to any one that fliall confider that hereby, firfr, I 
avoid that grand inconvenience wherewith all ancient and 
- modern obfervations have been per'plext , and as to Parallax 
infignificant,and that is the refraclion of the Air or Atmofphere. 
How great an inconvenience that was is obvious , face 'tis cer- 
tainly much greater at one time then another, and never at 
any certainty:, and fecendly, Tis not equally proportionable, 
for fometimes the refraclion is greater at feme diftance above 
the Horizon, then in or nearer to the Horizon it feif , and fome- 
times the quite contrary, which I have very cfrcn ebferved ^ 
and this to fo exorbitant a difference J as to confound all Hy- 
pothetical Calculations of Tables for this purpofe. This a- 
; rifeth from the uncertain and fudden variations of the Air or 
Atmofphere, either from heat and cold, from the thickrfefs -and 
thinnefs of Vapours , from the differing gravity and levity, 
from the winds, currents, and eddyes thereof, all which be- 
ing not fowell underftood by what way, and in what degree, 
and at what time they work and operate upon the Air, muft 
needs make the refraction thereof exceedingly perplext, and the 
reduction thereof to any certain theory fit for pra#ice,a thing 
almofr impoffibJe. Now if we are uncertain what part of the 
obferved Angle is tobeafcribed to refraction, we are uncer- 
tain of the whole obfervation as far as. the poffible uncertainty 
of reftaclion. Let me have but the liberty of fuppollng the 
refraction what I pleafe,and of fixing the proportional decreafe 
thereof according to the various elevation of the Rayes above 
the Horizon; I will with eafe make out all the vifible Pheno- 
mena of the Univerfe, Sun, Moon, and Stars, and yet not Hip- 
po fe them above a Diameter of the Earth diftant. Now in this 
obfervation there is no refraction at all, and confequentJy be 
the Air thicker or thinner;, heavier or lighter, hotter or cold- 
er, be it in Summer or Winter, in the night or the day, the 
ray continually pafleth direfijy, and is not at all refracted avd 
deBt&cd from its freight paflage. In the next place, by. this 
way of obferving I avoid all the difficulties that attend the ma- 
nounting; and managing of great Inftruments : Fori' 

have 



have no need of Quadrant, Sextant, or Odfcmc, nor of any o- 
ther part or Circle bigger then a Degree at mdft$ nor have I 
need to take care of the divisions and fubdivifions thereof, nor 
of the fubftance whether made of Iron , Brafs, Copper, or 
Wood , nor whether the parts thereof flirink or fwell , or bend 
or warp, to all which the be ft Inftruments hitherto made life 
of, have been fome wayes or other Jyable. And notwiih- 
IranqiHg the vail care and expence of the noble ticho about the 
making, fixing, and ufing his great Inftruments ; yet I do not 
find them fo well fecured from divers of thefe inconveniences 
but that they were ftiilTubjetf to Tome confiderable irregulari- 
ties, Nay, Rotwitfaftanding the feemingly much greater curio- 
fity and expenfe of Uevelim , and his infinite labour and di- 
ligence in the compleating and ufing of his vaft Apparatus of 
Agronomical Inftruments,. I do not find them fo we/1 fecmed 
but that fome of the caufes of errors that I have before men- 
tioned^ may have had a confiderable effed upon them a'fo; e- 
fpecially if they were fuppofed to meafure.an Angle to fome 
few Seconds , as I (hall hereafter perhaps have more occafion 
tomanifeft. Now, if the Inftruments of ticho and Uevelim, 
("who had certainly two of the mpft curious and magnificent 
Colle&ions of Agronomical Inftruments that were ever yet 
got together or made ufe of) were fubjed to thefe uncertain- 
ties, What ihall we fay of all that other fa rrage of trumpery 
that hath been made ufe of by mpft others ? We fee there- 
fore theneceflltyofthe conjunction of Phyfical and Philofo- 
phical with Mechanical and Experimental Knowledge , how 
lame and imperfeft the itudy of Art doth often prove without 
the conjun&ion of the ftudy of Nature ,■ and upon what ra- 
tional grounds it was that Sir John Cutler, the Patron and 
Founder of this Letfure, proceeded in jjyning the contempla- 
tion of them both together. • 

The next thing was the Inftrument for the making of this 
obfervation, fuchaoneas ffcould notbeiyable to any of the 
former- exceptions , nor any other new ones that were confi- 
de able, To this purpofe I pitched upon a Telefcope, the 
largeft I could get and make ufe of , which I defigned fo to 
fix upright, as that looking directly upwards, I could be a- 
bje certain'y to obferve th^ tranfits of any Stars over or near 

the 



07) 
the Zenith, and furnifhing it with perpendiculars and a con- 
venient dividing Jnftrument, I fhould be able not only to 
know exactly when the Star came to croft the Meridian , but 
alio how far it croffed it from the Center or Zenith point of 
Grejbam Colledge , either towards the North, or towards the 
South. All which Particulars, how [per formed , Hhall now 
in order defcribe, and this fomewhat the more diftintfly , 
that fuch as have adefiretodo thelike , may be the more rea- 
dy and fetter inabled to proceed with the fame. 

Fteft then (finding a Tube would be very troublefome to the 
Rooms through which it paft, efpecially if it were p'aced 
pretty far in the Room, and that one wanted fofree an zcccfs 
as was neceflary if it were planted nigh the wall , and that 
there was no abfolute neceflity of fuch an intermediate Tube, 
fuppofing there were a cell to dired the eye fixe to the Eye 
Glafs, and that there were Tome fliort cell to carry the Objeft 
Glafs in at the top , foas to keep it fready , whenraifed upward 
or let downwards, the light in the intermediate Rooms nor at 
all hindring, but rather proving of good ufe to this purpofe 
for feeing the Menfurator) I opened a palTage of afcout 
a foot fquare through the roof of my lodgings ( fee the Fourth' 
Figure) and therein fixt a Tube a a perpendicular and uprighr, 
of about ten or twelve foot in length , and a foot fquare, fo as 
that the lower end thereof came through the Ceiling, and was 
open into the Chamber underneath : This Tube I covered with 
a lid at the top q, houfed fo as to throw off the rain , and fo 
contrived,as I could eafily open or fhur it by a fmall firing n o p, 
which came down through the Tube to the place where I ob- 
ferved. Wichin this perpendicular Tube a a, T made ano- 
ther fmall fquare Tube b b, fit fo as to Aide upwards and down- 
wards, as there was occafion, and by the help of a skrew to be 
fixt in any place that was neceflary : Within this Tube in a con- 
venient cell c, was fixt the Objeft Glafs of the TelcfcopeCthac 
which J made ufe of was thirty fix foot in length , having none 
longer by me, but one of fixty foot, and fo too long to be made 
ufe of in my Rooms ) the manner of fixing which was this : The 
Glafs it felf was fixed into a cell or frame of Brafs, fo exadly 
fitted to it , that it went in ftiff; and to fill up all the Inter- 
im's, there was melted in hard Cement ; this cell had a 

D fmall 



Ci8) 

fmall barr that croffed under the center of the Glafs, or the a- 
perture thereof 5 in which barr were drili'd two fmall holes at 
equal diftance from the middle of theGJafs , , thro gh which the 
upper ends of the two perpendiculars d d were faftned $ and 
in the fixing this brafs cell or fame into the fquare Tube that 
was to $ide up and down , care was taken to make the barr lye 
as exaftly North and South as could be, . though that were not 
altogether foabfolutely necefTary to this obfervaticn. Thefe 
perpendiculars dd faftned to the barr hung 36 foot and better 
in length, and had at the lower ends of them two balls of lead 
ee as big as the Silks could bear, by which the loweft parts of 
this Jnftrument were adjufted , as I fhall by and by explain. 
But fir/1, I muft acquaint the Reader,that I opened aTo perpen 
dicularly under this Tube a hole rr a foot iquare in the floor 
below-,., which With fhutters could be clofed or opened up- 
on occafion 5 by this means I had a perpendicular Well-hole of 
about forty foot long, from the top of a to the lower floor ss* 
Upon the fecond floor s s I fixed the frame that carried the Eye- 
glafs and the other Apparatus fit to make this obfervation. I 
made then a Stool or Table, fuch as is defcribed in the fame 
'Vourth.Figureihh\ 9 having a hole through the top or cover 
thereof h h, of about nine inches over ; the middle of which I 
placed as near as I could perpendicularly under the middle of 
the Objeft Glafs in the cell-above, and then nailed the frame faft 
to the floor by the brackets i i, that it could not ftir ; under- 
neath the cover of this Table I made a Aider g g, in 
which was fixed in a cell an eye Glafs f , fo as that I could 
through the eye Glafs moved to and fro, fee any part of the 
hole in the Table that I defired , without birring th^ftool from 
Its fixtnefs. This was necefTary, becaufe many Stars which were 
forerunners of this Star in Draco, and ferved as warning to 
prepare for the approaching Star, went pretty wide from the 
parallel that pafTed over our Zenith} by this means alfo I took 
notice of the Star it fdf, at above half a degree diftance from 
the Zenith to the Eaft , and fo followed the motion of it with 
myeyeGlafs^ and alfo with my meafuring Clew, and at the 
fame time told the Seconds beat by a Pendulum Clock, and fo 
was very well prepared to take notice of all things necefTary to 
compleac the obfervation, but might have been otherwife fm> 
« prifed 



prifedby the fuddain approach and fwift motion ©f the laid 
bur. Thetneafurmg Jnftrament or Menfarator was around 
thin plate or circle of Brafs, delineated in the Seventh Figure, 
the aperture a b of which was about nine inches over, croffed 
m the middle by two very final] hairs a b and cd,which ferved 
to fliew the Zenith point at e, by which the Star was to pafs ; 
■there wereaWb two other/mall hairs fg and i h drawn parallel 
to that which was to reprefent the Eaft and Weft line, that paft 
under our Zenith, theft cut the Clue that reprefented the Me- 
ridian, or North and South Line at the places k andl , where 
the perpendicular points were made bv the two long plumb 
lines: This Inftrwment was produced on the fide a to n, n e 
being made fifteen times the length of em, To that e m being 
one inch and two thirds, en was twenty five inches: at n the 
line ne was croft by a ru'eof about 3 i-foot long op, which 
from the point n was divided each way into inches and parts, 
each inch being fubdivided into thirty parts, which ferved to 
determine, though not precifely, the Seconds on the line cd, 
for a minute of a degree to a thirty -fix foot Glafs, being very 
near one eighth part of an inch, and this eighth part, by the 
help of the Diagonal, being extended to two whole inches upon 
the three toot Rule op, it became very eafie to divide a part 
■Qtcd,;whicbfubtendeda minute into Tixty parts, and confe- 
quently to fubdivide it into Seconds. Now though the fixti- 
eth part of an eighth of an inch be very hardly di'ffinguifliable 
bv the naked eye ; yet by the help of looking 'through the Bye- 
glafs placed in the cell, md fo magnifying the Objefls at 'the 
Menfarator more then fix teen times ; 'tis eafie enough to dtflrin- 
mflnu But to proceed, J had one final 1 arm mt in- the Men- 
Jumor, to which the Diagonal thred was faftried'Wrhe point 
m 3 which ferved for the more nice fubdivlfions into Seconds « 
The other Diagonal thred which was Fafhied at n, ferved for 
fuch obferotions where fo great nicene'fs was not fo neceflary 
diftinguMhing only every four Seconds, The points where theft 
Diagonal threds were faftned , were exactly over the Hue ab, 
andthediftanceg em and eu were anlnchand two thirds. and 
fivainches. '". 

Therejarpmewhatof niceneft reqiiifite to the fixing -theft 
Diagonal threads fwhich is very material) at m and u 5 and that 



D 2 



IS 



is that there Be afmall fpringing flit to pinch the hair faft ex- 
actly over the line a,b , fo that the point of its motion may be 
precifely in the faidEaft arid Weft line,, and not fometimes in 
it, and fometimes out of ir ?9 which it is apt to be, if the Diago- 
nal line be .fixt in a hole, and move round. in it. 

This was the Menfurator by which I meafured the exaft di- 
ftance of the Stars from our Zenith ; it may be alfo made ufe of 
for the meafiiring the Diameters of the Planetsjfor theexamining 
the exaft diftances of them from any near approaching fix tStars, 
for meafuring the diftances of the Satellites of Jupiter and &- 
turn ft om their difeks, for, taking the diameters and magnitudes 
of thefpotsof the Moon,,, and for taking the diilances of ap- 
proaching Scars, and for many other menfurations made by Te- 
lefcopesorMicrofcopes, if it.be fo placed as to be in the fo- 
cus of: the Objefi Glafs and Ey e Glafs* I could here defcribe 
at leaft thirty other forts , fome by the help of fcrews, others 
by the help of wedges,fome after the way of proportional Com- 
pafTes,others by wheels, ethers by the way of the Leaver, others 
by the way of Pullies, and the like; any one of which is accu- 
rate enough to divide an inch into ioo, iooo, i oooo parts if 
it be neceflary ; but I muft here omit them, they being more 
proper in another place, . and fhall only name one other, becaufe 
I fometimes made ufe of it in this obfervation, which is as fim? 
pie and plain as this I have defcribed, and altogether as accu- 
rate ; but for fome accidental circumftances in the place where 
I made my obfervation , was not altogether fo convenient as the 
former.. This Menfurator then is made thus: take a Rule of 
what length it feemsmoit convenient for the prefect occafion , 
as two, three, or four foot long , . reprefented by a b in the 
Eighth Figure ydWidt this into .ip.o, 1000, ioooo equal parts, 
with what accuratenefs "'tis poflibIe,berween the points a b. On 
the top of this Rule, at; each end fix two crofs pieces gh 
and e f , then from the two crofs pieces e f and g h, ftrain two 
very fine and even clues , as Silkworms clues , curious fmall 
lrairs, or the like, , fo as that they crofs each other at n, and be 
diftantat o andp, an inch, or any other certain meafure defi- 
red. Let this Rule,bezelled on each fide, flip in a frame be- 
tween two cheeks qandr, upon the top of which ftrein ano- 
ther fmall hair as s t. This frame muft be faftned.ro the Te- 

lefcope, 



(21) 

iefcope, fo as st may lye inaduepofitiontothe EyeGlafsof 
it. Now in the time of obfervation the frame q r being fan- 
ned to the Telefcope as above , by Aiding the Rule ab to 
and fro, you give upon the line st any length defired, which 
is noted out by the line s t upon the rule ; for if o p be 
put one inch, then x y will be ^g of an inch , and if o p be 
thefubtenfe of r o minutes , then x y will be the fub:enfe of 
4I94 ; this is fo plain, fnnple, and eafie, that as any ordi- 
nary Workman will be able to make it , f I doubt not but e- 
very Reader will , without more application, underftand both 
the defcription and ufe thereof. I (hall return therefore to the 
defcription of the former Menfuraton 

The- next thing then is the way of fixing this Menfurator , fo 
as to fet the threads in their due pqfture , that is Eaft and Weft, 
and North and South , and that they cut each other un^er the 
middle of theGlafs.This laft was that which had the moft of dif- 
ficulty in the whole Experiment* For the performing of this , I 
removed the Aider underneath the Table that carried the Eye- 
Glafs, and alfo the Menfurator, and furlered the plumb lines to 
hang down through the aperture of the Table, and that the Balls 
might come the fooner to their perpendicularity, I fuffered 
them to hang into a vefTel of water , deep and wide enough, 
that they might not touch either fide or bottom. 

This expedient of hanging the plumbets in water I mentior 3 
becaufe without it 'tis not to be imagined how much time is 
loft by expectation of the fettlement of the faid perpendicu- 
lars, and how very apt they are to be made to vibrate by the 
little imperceptible motion of the Air, and by any fmall hair v 
or other impediment how apt to be put out of their perpen- 
dicularity : which by the way makes me very fearfjl that all 
common Inftruments have hitherto been lyable to very great 1 
errors, by the unaccurate hanging of their plumb lines, being 
made for the moft part to hang and play againft the fide of the 
Inftrument. By this means they would fbon come to hang per- 
pendicularly , and be fo detained when in that pofture ; not 
being apt to be ftirred by the motion of the Air, or t heir own ' 
fwing-, and whilft thus fteady , I fixed two fmall arms of Braf \ , 
fuchas aredefcribed in the Seventh Figure by z z , z z, which 
had fmall holes at the^xtreams, withaimall flitonthe fide to 

admit, c 



(22) - 

admit or emit the plumb line as there was occafion 5 one of theft 
is more at large defcribed in the Sixth Figure, Now the plumb 
line being let into the middle of, this,! did with all the accurate- 
nefs I couidfo fix thefaidarm, that the plumb line pail exact- 
ly through the middle of the bole y. When I was fuffidently Sa- 
tisfied that the plumb line 3 paft cxadly through, the middle of 
the trying arms, I fixed thofe arms zz,z.2, and removed the 
plumb lines, then I laid the Menfurator 1 1 in -the Fourth Fi- 
gure, upoiuhefurfaceof the Table, and took great care that 
the crofTes k and J in the Seventh Figme^hygxMy under the 
middle of the holes in the arms, which having done by the 
help of certain fcrews , I fixt the Menfurator faft 1 the Tabje s 
and prepared for the obfervations, putting in the Aider gg 
in the Fourth Figure^ that carried the cell f, and lying down 
upon a Couch (k of the Fourth Figwe) made purpofely for 
this "obfervatioii, I could look di redly upward , 5 and -with my 
left hand move the Cell and Eye Glafs fo as to find any Star 
which palled within the hole of the Table, and at the fame time 
with my right hand I could move the Diagonal thread (r mof 
the Seventh Figure) foas tofindexadly how far diftantfrom 
the Zenith e ? . either. Northwards or Southwards^the Stars, paft 
the Meridian d c , and giving notice to my Afllftant to prepare* 
he upon -the fign given took notice exaftly by a FendqlumOock 
to the parts of a Second when the faid Stars pa-ft , and alfo took 
notice what divifion the Diagonal thread m t cut upon the 
: Rule o p, 

With all thefe difficulties,- I was forced to adjuft the In* 
ftmnien t every obfer-va.tion I made^bath before and after it was 
made, which hath often made me-. wifli that I were near fome 
great and folic! Tower , or fomv great Rock or "deep wdl,tbat 
fo J might fix, all things at once, and not be troubled continu- 
ally thus to adjuft the parts of the faid Instrument.; for who- 
ever hath that opportunity ..will., I queftion not, • efpecially if 
the lines of hh Meofurator be made. of the fingle clues of aSilkr 
worm, with much tafe difcoyer plainly a change of the diflanee 
of Sears of the greater magnitude from the Zenith, in a much 
flioner rime then fix moneths. This variation alfo will be 
much more eafie to be difcovered , if inftead of a thirty fix 
foot Glafs # there be made ufe of one of four times that 

length,, 



length, to mt K one of one hundred fourty four foot>-and if 
inftead of a Tower fome deep and dry Wei! be made life of, fiich 
as I have Teen at a Geritlemans hoiifenot far from Bmfied Downs 
in Surry y which is dugg through a body of chalk, and is near 
three hundred and fixty foot deep, and'yet. dry almoit to the 
very bottom: Forfucha one is much lefs fubjed to any kind 
of alteration , either from the fettling towards this or that fide, 
which moft Towers and high Buildings , whether new or old, 
arelyableto: This alfo is fafe from bending and fba king with 
the r wind, which 1 find the itrongeft Hou fes, Towers, and 
Walls ^ if of any considerable height, are apt to do, nor 
would the wind hav'e^any power to fwerye the perpen'c'icular,% 
which 'tis almoft impOiTible to prevent in high Buildings a- 
bove ground. But this I can only wifii it were performed, 
but cannot hope to have any opportunity of Doing it my felf. 
But certainly thedifcovery of the observation will abundantly 
recompenfe thofe that have the curiofity to make it. 

Having thus refolved upon the way , and prepared the In- 
firumenis fit for the obfervation, I began to obferve the Tran- 
sits of the bright Stair in the head of Draco \ and alwayes botjj . 
bef@re and after the obfervation , I adjufled the Menfurator by 
the Perpendiculars, that I might be the more certain of the 
exafinefsof the Jmlrument 5 for I often found that when I came 
*6 examine the Inftrument, a day, or two, or three, or more, 
after a former obfervation , that there had been wrought a 
confiderable change in the Perpendiculars , in fo much as to 
vary above a minute from the place where I left them , which I 
aforibe chiefly to the warping of the Tube that rofe above the 
roof of the Houfe ,' finding fenfibly that a warm day wcu'd 
bend it cortfiderahly towards the South , arid that a moift Air 
would make it bend from the quarter of the wind: But yet I 
am apt to think there might be fomewhat alfo of that variation 
afciribable to the whole Fabrick of the Roof , and pofllbly alfo 
toTome variation of the Floors ; but yet I never found thefe 
variations fo fudden, as to be perceptible in the time of a fingle 
obfervation, finding al waves the preceding and fublequau 
adjuftings to anfwer. 

Th£ firft obfervation I made was the Sixth oi Jdy, 1669. 
when I obferved thebrightStar of Draco to pafs the Meridian 

Northwards 



Konhwarclsof the Zenith point of the Menfurator, at about 
two Minutes and twelve Seconds. 

The fecondobfervation I made was upon the Ninth of 7u% 
followmg, when I found it to pafs to the Northwards of the faid 
Zeni th or crofs of the Menfurator , near about the fame place , 
not fenfibly differing. 

The third obfervation I made upon the Sixth of Jugufi fol- 
lowing 5 then I obferved its tranfitus North of the aforefaid 
Zeni tli, to be about two Minutes and fix Seconds. 

Thelaftobfervation I made upon the One and twentieth of 
OBober following , when I obferved it to pafs to the North of 
the Zenith, at one Minute and about 48 or $0 Seconds. 

Inconvenient weather and great indifpofition in my health, 

hindredmefrom proceeding any further with the obfervation 

that time, which hath been no fmall trouble to me, having an 

extraordinary defire to have made other obfervations with much 

more accuratenefs then I was able to make thefe , having fmce 

foundfeverahnconvenienciesinmy Tnftruments, which I have 
now regulated. 

Whether this Zenith fo found out upon the Menfurator , be 
^the true Zenith of GreJhamColledge, is not in this inquiry very 
material (though that alfo I defigned to examine, had not an 
unhappy accident broken my Object Glafs befcre I could com- 
p'eat the obfervation) for whether it were, or were not, it is 
certain that it al wayes had the fame pofition to the true Zenith , 
the Objeft Glafs and Perpendiculars having not been in all that 
time removed out of the Cell, whence if the faid Objedt Glafs 
were thicker upon one fide then upon t^e other (which is very 
common and very feldomeotherwife) and confequently defle- 
cted the ray towards the thicker fide, and fo made the Perpendi- 
cular of the Menfurator to lye on that fide of the true Perpen- 
dicular , that the thicker fide of theObjeft Glafs refpeftedjet 
it being al wayes fo if the tranfitus of the Star varied from this 
falfe Perpendicular , it muft alfo vary from the true one. The 
manner how I defigned to examine and find out the true Perpen- 
dicular, is this, which is the way alfo of adjufting of Telefcopi- 
cal fights, as I fliall afterwards have occafion tofhew. Having 
marked the four fides of the Glafs, the North with N, the Eaft 
withE, the South with S, and the Weft with W, about the firft 

of 



(2$). 

of June I begin to obferve and meafure the true diftance of force 
remarkable fixt Star, as of this of Draco from the Zenith found 
one night when the fide N of the Glafs flood North. Then I change 
the fide of the Object Giafs , and put the North fide South- 
wards, and the South, Northwards, and obferve the Tranfitus 
of the fame Star the next night, and note down the fame; the 
third night following I put the Eafl fide or E Northland obferve 
the tranfit of the fameS^r over the Meridian ; and the fourth 
night J p.uc the Weft fide or W North, and obferve the tranfit of 
the faid Star. Now by comparing all thefe together, it will be 
very eafie to deduce what the falfe reflation of the Objecl: Glafs 
is, and which way it lyes, and confequentlv to regtfate the ap- 
parent Zenith by the true one. But this only by the by. 

'Tismanifeftthenby theobfervations of July the Sixth and 
Ninth : and that of the One and twentieth of 0#*for,that there 
is a fenfible parallax of the EarthsOrb to the fixt Star in the head 
of Draco,, and confequently a confirmation of the Copermcan Sy» 
item againft the FtolowaickandTichonich 

Before 1 leave this Bifcourfe , 1 muft not forget to takenotice 
of iome things which are very remarkable in the laftobfervation 
r made upon the 2 1 oWtfoher. And thofe were thefe. Firft, that 
about 1 7 minutes after three a-c!ock the fame day, the Sun be in* 
then a good way above the Morizon, and fliining very clear into 
tiie Room where I lay to obferve, and having nothings fcreen 
oft the rayes of light, either in the .Room where I was , or in tht 
next Room through which f looked, I obferved the bright Star 
in the Dragons head-to pafs by the Zenith as diftinflly and clear- 
ly as if theSun had been fet,though Imuftconfefs it had loft much 
or the glaring brightnefs and magnitude it was wont to have in 
the night, and its concomitants were vaniflit : The like I found 
it divers otherdayes before, when I obferved it, the Sun fthjifjg 
very deer into both the aforefa id Rooms , which by the Way ! 
fuppofe was the firft time that the fixt Stars were fee n when the 
Sun Aim d very bright, without any obfcuring of its light by E- 
clipfe or ctherwife. And though we have a great tradition that 
the Stars may be feen with the naked eye out of a very deep Well 
or Mine in the day, yei J judge it impoffible, and to have been a 
meer.fiftion, without any ground; For the being placed ar the-bot- 
torn of a Well doth not at all take away the light of the 
Sphere rrom atedting th€ eye in and near theAs 



indeed the fides thereof may much takeoff the lateral rayes; but 
unlefs the radiation of the falfe rayes of the Star be brighter then 
that of the Air, the true rayes from the body are fo very final 1 , 
that 'tis impoffible the naked eye fhould ever be affected by 
them. For in the fecond p!ace,by this obfervation of the Star in 
the day time when the Sun Alined, with my 3 G foot Glafs I found 
the body of the Star fo very final! , that it was but fome few 
thirds in Diameter,all the fpurious rayes that do beard it in the 
night being cleeriy fhaved away 5 and the naked body thereof left 
a very fmail white point. 

The fxal nefs of this body thus difcovered does very 
fully anfwe'r a grand objection alledged by divers of the 
great Ant i-eofer -nicms with great vehemency and inftiking 5 
amongft which we may reckon Bkciolv* and Tacquet , who 
would fain make the apparent Diameters of the Stars fobig, 
as that the body of the Star fhould contain the great Orb many 
times, which would indeed fwell the Stars to a magnitude vaftly 
bigger then the Sun, thereby hoping to make it feem fo impro- 
bable, as to berejetfed by all parties. But they that fnall by this 
means examine the Diamet*er of the fixt Stars, will find them fo 
very final 1, that according to thefe diilances and Parallax they will 
not much differ in magnitude from the body of the Sun, fome of 
them proving bigger, but others proving- lefs ; for the Diameter 
of the parallaclica' Circle among the fixt Stars, feems to exceed 
the Diameter of the Star ahnoft- as much as the Diameter 
of the annual Orb of the Earth 'doth that of the Sun, 
And poflibly longer and better Telefcopes will yet much dimi- 
nifih the apparent bulk/of the Stars by bringing fewer falfe rayes 
to the eye that are the.occafion of the glaring and magnifying of 
the faid bodies. It may for the prefent fufifice to fhew that even 
with this Glafs we find the Diameter of this Star confiderably 
final ler then a Second , and the Parallax we judge may be about 
XI or 30 Seconds.lt will not therefore be difficult to find many 
S'ars whofe Diameters fiball be lefs then a two hundredth part of 
this Parallax, as poffib'y upon more accurate obfervation this 
very S'ar may be found to be* Now we find that the Diameter 
of the Orb of the Earth is but two hundred times bigger then the 
Diameter of the Sun in the Center thereof 5 and therefore if the 
paralladical difference be found to be two hundred times more 
then the vifible Diameter of the Star, the Star will prove but of 
the fame magnitude with the Sun. This, 



(27) 

This Difcovery of the poffibihty and facility of feeing the- 
fixt Stars in the day time when the Sun fhines, as I think it is the 
firftinftance that hath been given of this kind,fo I judge it will be 
a difcovery of great ufe for the perfecting Aftronomy ; as firft , 
for the rectifying the true place of the Sun in the Eclipcick at 
any time of the year 5 for fince by this means 'tis eafie to find any 
Star of the firfl, fecond, or third magnitude at any time of the 
day, if it be above the Horizon, and not too near the body of 
the Sun: And fince by a way I fliall fhortly publifh any Angle to 
a Semicircle in the Heavens, may be taken to the exaclnefs of a 
Second by pne. (ingle obfervator; It will not be difficult for fu- 
ture Obferva tors to redifie the apparent place of the Sun a- 
mongft the frxt Stars to a Second, or very near, which is one 
hundred times greater accuratenefs, then has hitherto been at- 
tained by the beft Aftronoraers. The like ufe there may be made 
of it for obferving any notable appulfe of the D, 1^,}?, ^, and?, 
to any notable fixe Star that fhall happen in the day time,wfcich 
may ferve for difcovering their true places and parallaxes. The 
Refractions alfooftheAir in the day time may by this means be 
experimentally detected. 

J fhould have heredefcribed fome Clocks and Time-keepers 
of great ufe, nay abfolute necefllty in thefe and many other A- 
ftronomical obfervations,. but that I referye them for fome at- 
tempts that are hereafter to follow, about the various wayes I 
have tryed, not without good fuccefs of improving Clocks and 
Watches, and adapting them for various ufes, as for accurating 
Aftronomy/ compleating the Tables ofthefixt Stars to Seconds, 
difcovery of Longitude,regulating Navigation and Geography' 
dete&ing the proprieties and effects of morions for promoting 
fecret and fwift conveyance and correspondence, and many ci- 
ther confiderable Scrutinies of nature: And (hall only for' the 
prefent hint that I have in fome of my foregoing obfervations 
difcovered fome new Motions even in the Earth it felf, which 
perhaps were not dreamt of before, which I fhall hereafter more 
at large defcri be, when further trya's have more fully confirmed 
and compleated thefe begintngs.At which time alftlflial! explain 
a Syftem of the World differing in many particulars from any yet 
known , anfwering -in all things to the common RulesofMecha- 
nical Motions : This depends upon three Suppositions. Fir/*, 
That all Cceleftial Bodies whatfoever, have an attra&ion or gra- 

E' 2 Virata 



••*cr towards their ov;n Cencers,whereby they at trad 
nor on 1 }' tjieir own parts, and keep them from flying from 
them, as we may obferve the Earth to do, but that they do alfo 
attract a'l 1 the other Cceleitial Bodies that are within the fphere 
of their a&ivity ; and confeqnently that not only the Sun and 
Moon have an influence upon the body and motion of the Earth, 
and the Earth upon them, but that- S alfo &£>fo and ¥ by their 
attractive powers, have a confiderable influence upon its motion 
as in the fame manner the correfponding attractive power of the 
Earth hath a confiderable influence upon every one of their mo- 
tions alfo. The fecond fuppoiition is this,That all bodies what- 
foever that are put into a diretl and -Ample motion, will fo con- 
tinue to move forward in a ftreight line, till they are by fome o- 
ther efFedual powers defleded and bent into a Motion, defcri- 
bing a Circle, EUipiis, or fome other more compounded Curve 
Line. The third fuppoiition is, That thefe attractive powers 
are fomuch the more powerful iryoperaung, by how much the 
nearer the body wrought upon is to their own Centers. Now 
what thefe feveral decrees are- 1 have not yet experimentally ve- 
rified ; but it is a notion, which if fully profecuted as it ought 
to be, will mightily aflift the Aftronomer to reduce all the Cce- 
leftialMotions to a certain rule,which I doubt will never be done 
true without it. He that understands the nature of the Circular 
Pendulum and Circular Motion, will eafily underftand the whole 
ground of this Principle, and will know where to And directi- 
on in Nature for the true flaring thereof. This I only hint at pre- 
lent to fuch as have ability and .opportunity of profecuting this 
Inquiry, and are not wanting of Induftry for obferving and 
calculating, wiihing heartily fuch may be found, having my felf 
many other things in hand which 1 would firft compleat , and 
therefore cannot fo well attend it. But this I duicft promife the 
Undertaker, that he will find all the great Motions of the World , 
tobe influenced by this Principle,and that the" true underftand- 
in? thereof will be the true perfection of Aftronomy, 



I O'N D N, 
Printed for John Mmjn, Printer to the Royd Smety, 1674. 



ANIMADVERSIONS 

Onthefirft pare of the 

MACHINA COELESTIS 

Of the Honourable 3 Learned,and defer vedly Famous 

Aftronomer 

JOHANNES HEVELIVS 

CONSUL OF 

DANTZIC 

Together with an Explication of fome 

NSTRUMENTS 



M A D E B Y 



ROBERT HOOKE, ProfefTor of 

Geometry in Grejham College , and 

Fellow of the Royal Society. 



LONDON, 



Printed by T.R, for John Umyn Printer to the Royal Society. 
at the Beti in St.Pauls Ghurch-yard, 1 6 74. 



■■■HMHOH^HHHMr" 



"£$» «35». *$» -. 




THE 



^ 







Ti/ £ Reafon of the prefent ^nimadver/ions. page r • 

How far He veii us has proceeded, That his Infiru* 
ments do not much exceed Ticho. The bignefs, Sights and Di- 
vifions, not eonfiderably differ iwg k Ticho not ignorant ofhk 
new wAyofDivijion. p,2. 

V roved by fever al faff ages out of his Works, p. f , 4, 

That Jo great curioptyas Hevelius ftrives for is needless with- 
out the ufe ofTelefcopical Sights, the power of the naked eye being 
limited, that no one part of an Inflmment fhould be moreperfeU 
then another. p-4,5* 

Hevelius his Letter of 16^5. with his opinion of Tele fcopical 
Sights. p.S,6. 

That if Hevelius could have been prevail" d on by the Author to 
have ufed Tele fc ope Sights, his Qbfervations might have been 40 
times more exact then they are ¥ p 6\ 7* 

• That Hevelius his Objections again ft Telefcope Sights are of no 
validity^ but that Sights without Telefcope s cannot diflinguijh A 
lefs Angle thenhalf a Minute. P»7- 

That an Inflmment of 3 foot Radius with Telefcopes, will d$ 
more then one ofjfcorefoot Radim with common Sights, the eye 
being unable to diflinguijh. This is proved by the undifcernMe- 
nefs of Jpots in the Moon, and by an Experiment with Lines on a 
paper, by which a Standard is made of the power of the eye. p. 8. 
That it had been much to be wijht that Ticho and Hevelius 
had, and that Obfervapors for the future would ', well confider 
this. p. 9 ^ 

a z Jhat 



The Contents* 

V% tt, and on the difficulty acknowledged of taking Stars Di* 
flames from the Moon and Sun, and a way promt fed of doing them 
with more safe. p, 3 8. 

the fee wing difficulty and even impoffibility of taking 3 jeveral 
Diflances m the Heavens, without failing one Second, and the 
reafen why 'tis more likely that there could not he a greater certain- 
ty then of\ Minutes in the whole,, ibid. 

Heveiius his Letter concerning my Animadverfion^ and about 
Telefccp ncal Sights. P«3M°»4 I * 

An jinfwer to it. p. 4 f , 4 2 , 4 3 \ 

A Conclufion of the Animadverflons. That the learn" d World 
is obligd to Hevdiusfor what he hath done, hut would have been 
more, if he had ufed other Inflruments* ' ' p. 4 3 , 4 4 . 

That the Anim&dvertor hath contrived fome hundreds of In* 
fl ruments, each of very g re at accuratenefs for taking Angles, L e- 
vels, &c. and a particular Arithmetical Inftrument for perform- 
ing all Operations in Arithmetick, with thegreatefleafe, fwift- 
nefs and certainty imaginable. P«44j4 5 • 

That the Reader may be the more certain of this, the Author 
defcribes an Inflrument for taking Angles in the Heavens , whofe 
perfe El ion more then common confljls, 1 . In the manife fling of the 
Sights. 2. In the Diviflons. 3* IntherefleSliveconflrucJion 
.of the Sights. 4, In its exact Perpendicularity, s- In it s fix- 
ation and motion fit for Ob fervations, 6. In its facility for wake ; 
and 7. Initscheapnefs. p. 4 5, 46. 

An Explication of the ma\e and lingular conveniences of thefe 
new Sights, p.46 5 47,4S. 

An Explication of the new way of Dividing, and the great 
advantages of it above others. P*48,49, 50. 

Made more eafie by the 'Explication of the Delineation in the 

1, 2, 3, 4, 5, 6, 8, 9, 10 , and 1 ith. Figures, expr effing the 

Frame, hollow Center, Moveable arm^ Screw-Frame , and 

• Screw for the Diviflons. The Obliquity of it to the Plain of the 

Quadrant, and the reafin thereof p. 5 r , 5 2 . " 

The way of certainly determining the Obliquity, and the re- 
folving the whole Quadrant thereby into one grand Diagonal, 
and the magnifying thereof in a duple, triple, decuple, &c. Pro- 
portion. P*53« 

Then follows a m>re particular Defcription of the Screw- 

Frame* 



The Contents 

Frame, its Getters \ Centers, Screws, Handles] Indices f Pinnion-' 
Divifions, &c. p. 5 3 , 5 4. 

How by thefe Indices is pointed out the Me afar e of the angle , 
in Degrees, Minutes, Seconds, &c. p. 5 5 . 

The great advantage of thefe new ways of ordering Sights ta- 
ken notice of. i b i d • 

And the whole Contrivance more particularly defer ibed. p. 5 6, 

And explain d by a Delineation, and the manner how they are 
applicable to a Quadrant or other Inftrument. p. 5 7. 

How they are made ufe of for taking an angle bigger then a 
Quadrant, is farther defer ibed, and made more intelligible by a 
Delineation* p . $ ' S * 

The way of adjuftingtht two fixt Sights, fo as to loohforwards 
and backwards exactly in a right Line, and how to adjujl and fix 
the Sight-Threads in the Tubes, with the reafon thereof p. 59, 60, 

A Defcription of the Water-Level, for fetting the hjlrnment 
exactly Horizontal. Some Difficulties, and the way of prevent- 
ing them propofed, p. 6 r , 6 2 . 

This Inffrument farther explained by a- Delineation, and the 
rtafon of its accuratenefs manifefted. p. 6 3 . 

Some Difficulties about the make of the Glares for thefe Le* 
vels, and fome Expedients propounded, together with other wafs 
and forms of Levels. p. 6 4,65 . 

After the Difficulties of Obfervations made the old ways are 
taken notice of follows the Defcription of a new Method of mov- 
ing and fixing Inflrumentsfor Obfervations, fo as to prevent and 
obviate them. p . 6 6 , 6 7 , 6 S . 

This is made more plain by aDelineation andExpiicathn* p, 6 9 . 

When the Circular Pendulum was fit ft invented and pub- 
lifht. p.69,70.: 

Here by the way is publifhed a Defcription of Wheel-work^ 
which maybe called the perfection of Wheel-work, having the 
perfect eft Idea that toothed Wheel- work is capable of performing 
the fame effect as if the Wheel and Finn ion had an indefinite 
number of Teeth, p. 7 o , 7 r . 

A farther Explanation of the Pole of Conical hole: of the 
axis* ■ p.72. 

A Defcription of the Frame for keeping the Inflniment ^ in its 
Perpendicularity, and yet always in the azimuth of the celefl/al ' 

Object y . 



The Contents." 

Qbf$, with a Bigreflionof the great ufe of this Principle iff 
Dialling, equalling time, Clock-work, &c, P>73- 

%ke way of fining an exatf right angle or Quadrant, more 
particdarly deferred ani explained. An Objection about the 
incfuluy of the Divifions anfwer'd. p. 74, 7 5 . 

Some Ufes of this Inftrument hinted : 1. For meafuring the 
Refratfibnoftheair. 2.For regulating the place of the fixt Stars. 
3. Of the FUnets. 4, For ftattng the Latitude of places. 5. For 
examining the influence of the Planets on the Eartk 6. For me a- * 
Turing a Degree, which was the caufe of its Contrivance. 7. For 
'tneafuring feen Diflances. i. For taking the Diameters of the \ 
~Sm, Moon and FUnets. ^ p. 77. j 

Where by the By are mentioned two other Inflrmnents ; one j 
"■for taking Diameters to Seconds ; and afeconifor looking on the 1 
■Body of the Sun, without harming the eyes. p. 7 3. 

A ninth Ufe for Levelling , &c. with afbort GoncL*- 
fon. ibidJ 



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SOME 



ANIMADVERSIONS 



On the jfirft Part of 



H E V E L I V S 
His MACH1NA COELESTIS, Sec. 




|AVING lately perufed a Difcourfe of Heveliu*, 
newly publ ifljed ,entituled,jW^#/j HeveliiMachina 
Coele fits, pars $>rior Qrganographiamjive inftrumento- 
rum Aponomicorum omnium quibus Autor haftenm 
jfdera rimatm & dimenfos eft ac cur at am delineationem ejr defer ip- 
tionem plurimis Uonibus £ri incifts iiiujlratam & exornatam ex- 
hibens, &c. and finding it a Difcourfe about practical and 
mechanical Knowledge, and of that kind wherein Geometry 
feems to be more then ordinarily concerned ; I thought it 
might not be ungraceful to my Auditory, ( nor improper to the 
Subject o/SV.JOHN CUTLER'/ LecJure, which is partly Mecha- 
nical and partly Fhyjical) to confider a little the Contents there- 
of : And fomewhat the rather too, becaufe having heretofore 
communicated to him fomewhat of thisSubject,which I had oc- 
cafion ro read in this place inone of my former CMTLBRIAN 
Le&ures, 1 6nd he hath made fome Animadversions and re- 
. flexions thereupon. 

A I 



CO 

I find then that this excellent Perfon hath been for the mofi: 
part exceedingly circumfpeft, to find out the inconveniences 
and difficulties that do accrew to the beft Obfervators, even 
with the beft inftruments, and has not been lefs induftrious to 
find out ways to obviate and overcome them 5 In the doing of 
which, he feems not to have fpared either for labour and vigi- 
lancy, or for any coll: and charges that might eiTefl: his pur- 
pofe, for which he hath highly merited the efteem of all fuch as 
are lovers of that Science : But yet if he had profecuted that 
way of improving Agronomical inftruments, which I longfince 
communicated to him, I am of opinion he would have done 
himfelf and the learned World a much greater piece of fer vice, 
by faving himfelf more then f of the charge and trouble,and by 
publishing a Catalogue ten times more accurate. For though 
I doubt not in the leaft but that he hath by his own extraor- 
dinary diligence, care and coft, corrected feveral miftakes 
and errors committed by the affiftants of the Noble Ticho : yet I 
am not fatisfied that his Inftruments are capable of making Ob- 
fervations more accurately then thofe ofiicho, though 'tis pof- 
fible they may do it with fomewhat lefs trouble and inconveni- 
ence. Forfirft, I find that thofe of Tick* were as large as 
thofe of Hevelm, and confequendy were capable of as accu- 
rate and minute divifions, and of as long and convenient Sights. 
Secondly, I find that the Sights made ufe of by Bevelim are 
the very fame, at leaft not at all materially differing from thofe 
of Ttcho, being only naked Sights, made by a flit and edge, 
ferving only to regulate the direction of the naked eye, but no 
ways capable ofa?fiftingthe eyetodiftinguifti more accurately 
the" objeft. Thirdly, I find that though the way of Divifion 
made ufe of by Bevelim , be a very ingenious invention, 
and that which is Geometrically true and certain, yet if we 
confider the great difficulty there is in Mechanically perform- 
ing it, wefhallfind it not much preferrable, if altogether as 
good as that of Ticho. And 'tis plain enough that Tuho him- 
felf was not ignorant of it, though his particular reafons why 
he made no more ufe of it, we certainly know not: a Tis very 
probable, becaufe he thought it not altogether fo accurate, as 
that he did make ufe of. For fomewhat to this purpofe he fays 
himfelf in thefecond Book of hisObfervaUonsofthe Comet of 

1577. 



(3) 

1577* pag. 4^ x * Hane graduum in fwguta mimfa , weaning 
the Divifion by Diagonal Lines ; & etiam horum in denafcrupuA 
fecundafubdivifionem in omnibus meis macbinis Jlfironomicis ujur- 
po, eo pod Warn multis ab bine annis exqmfitiffimam expert us fum. 
Licet enim ejus demonjlratio inRetfilweis paralielogyammis pro- 
pr'ie conveniat, mhilominus arcualibm etiam in tarn exili inter fti- 
tioquod* retfa line a in fenfibiliter differ t, citra omne err oris ve- 
(ligium convenient er applicatur. "*Tis true, Tick's Objection 
againftthis way of Divifion by Diagonals is materials to a Ge- 
ometrical accuratenefs, but his Anfwer to ic is altogether as 
material, that though it be not exaflly true, yetitdothinfenji- 
biliter differre, and foiong as the error is not difcovered by 
fenfe, there can be no error committed in obfervation ; and 
indeed the whole matter both one way and the other is infigni- 
ficatit, andbutavaincuriofity to endeavour to divide an in- 
ftrutnenc into feconds, or parts fmaller then a minute, foriflhall 
by and by ftew that the eye can hardly diftinguifli minutes in 
the object : But were fuch nicenefs of Divifion of any ufe, 'tis 
eafily enough to be done to Mathematical truth ; for as I fhall 
anonfliew, there is a certain diftanceof each of the parallel 
Circles, which being given, the ftraight Diagonal Lines will 
divide the degree, by the interfedion with thofe parallel Cir- 
cles, into exactly equal parts, which would have better an- 
fwer'd Tichos Objection,, had he known it, which 1 wonder, 
Iconfefs, how he could over- fee, fincehe feems to have fpent 
many thoughts on the matter ; but this only by the By, becaufe 
i (ball fpeak more at large of it afterwards. But he proceeds 
to this other way of Divifions, which he, as well asHevelius, 
afcribes to Nonnius, whereas the other that he approves of 
came firfl from England, as it appears by a palTage in another 
Book of his , where he difcourfes fomewhat of the fame 
Subject. 

• Altera Divijio ad clariffimi Matbematici Petri Nonni i in Li- 
bello de crepufculis propofitione tertia imitationem perplures qua- 
drantisarcus introrfum defcriptos , & diverftmode fubdivifos pro- 
cedit ; etfiautem in hac ipfa apprime ingeniofa Nonni i invent ion e 
aliqmd Autfmrii loco expeditius a nobis aUitum efl, itaut exte- 
rior arcHS inphrimas partiunculas dividatur, neq; is or do aut nu- 
merus annum fife 'introrfurn comomitantium quern ille prtfinivit 

A 2 fed 



(4) 

fed mult o expedhior & perfeut'ur objerveiur \ (/am apt to think 
he knew this very way, and here hints it :) tamenquia h<ec fab- 
tilitas cum ad praxin deventum eft flits habeat labor is quamfru- 
Bus, nequeidin rtceffu praftet quod prima front epollicetur, utali- 
biplemus cjlendemus.i'dcirco apudrnos dudumm ufu effe dejiit. 
From which words, and -alio from what he fays in his -firft 
Book ofthe new Scar in 1572, pag.671. fpea king of the com- 
parifon between thefe two ways of Divifions, to wit, Sitcu- 
jufiunq^ velit ingeniofa certe cfapfrime Mills eftdifiributio.quam 
& egopojiea arcualibus graduum divifionibus in quadrantibm fex- 
tantibu* & armillis.non inconcinm aut infrugifere applied. Li- 
cet enim demonftratio ejus infills reotilineis juperficiebus ad unguem 
fe habeat ; tamen cum quinornm vel denorum minutorum (patium 
in circumferentiis majufiulk a nftilineo infenjlbiliter differ at, 
hie quo ft ejus ufius fatis commodus & ratus ejfe poterit, multoq; 
Nonniana plurimorum arcuum intricata <jr difficili fubdivifione ex- 
peditior aptiorqs deprehenditur. From his Difcourfe I fay in 
thefe two places, and from feveral others difpers'd up and 
down his WorKs, which 'twould be too long now to quote, 
'tis evident tYnxficho was not ignorant of this way of Sub-divi- 
fion, fo much applauded by Hevelius, invented by Petrus 
Mnmus,.and promoted byf^himfelf; and yet we fee. he 
prefer'd that way of Diagonals, firit made ufe of in Englandby 
the mod skilful Mathematician Richard Cant zkr, before it, re- 
jecting the one and making ufe of the other in all his Instru- 
ments. But either of them will do well enough if the Divifi- 
ons be done with great circumfpection and care,, and inftru- 
ments of the fize of thofe larger ones both of Hevelius and It- 
ch, are capable of Divifions ten times moreaccurate then are 
needful for common Sights, be they never fo long, without 
making ufe of either Ticho's ov Hevelius 3 $ way of Divifion, 
the eye being unable todiltinguifhafmaller Angle. T^ what 
purpofe therefore is it to make the Divifions fo fine, or any 
one part of the inftrument or obfervarion more accural then 
another ? frace the power of dilringuifhing by the naked eye is 
that which bounds and limits all the other mcenefs, and what- 
ever pare is more curious then rhat can equalize, is of nollgni- 
ficancy. For inftance, in taking the altitude of a Star, it 
would be but labour loft to diftinguifli by the Diagonals, or 

otherwife 



C 5 > 

otherwife to Seconds, whilft in the mean time you are not cer* 
tain that the Plumb-line is true to a minute, or whilft you are 
not able to direct the Ruler, bearing the Sight s to a greater cer- 
tainty then to that of a minute. And the Jike might be faid of 
the extraordinary curiofity in any two parts, and the failure in 
any third, that is efTential to an obfervation } as fruitlefs it is 
to calculate to feconds, when the obfervations are not true to 
minutes, or to be certain by the Sights and Divifions to fe- 
conds, and uncertain in the Plumb-line to minutes. 

There is therefore one thing in Hevelim his Inftruments, 
that though they be never fo large, never fo accurately divi- 
ded, of never fb choice and convenient materials, and never fo 
tractable for ufe, and never fo skilfully and induftrioufly ufed, 
will notwithftanding make them all equal as to ufe, with one of 
about two or three foot radius ofmettal with Ticho's Sights 
and Diagonal Divisions, which is occafioned by the limited 
power of diftinguifhing by the naked eye. 

Something to this purpofe I communicated to Hevelim in 
the year 65. and hoped that / might have thereby fomewhat af- 
filed him in his great and laborious Work, firft by earing the 
eye, and next by making it capable ofdiftinguiftiing more ex- 
actly, 1 having hinted to him the way how to reform and obvi- 
ate that inconvenience by Telefcopical or Perfpeclive Sights, 
as alfo the way of making inftruments of much lefs bulk, to do 
ten times more then 'twas poffible to do with the largeft inftru- 
ments made the common way. In anfwer to v\ hich he returns 
me this Difcourfe, in a Letter to the Royal Society, in the 
vear6$.* 



D U S ille ohfervandi per Telefcopia adminkulo Sex- 
tantk vel ^uadrantis^ videtvr n(ihi vix adeb tutus, 
quam vulgar is, ft pinnacidia recfe ac j fie fikt affix a. H<ec enim 
Junt immobilia \ Telefcopia verb nulla ratione^adej firmiter affiai 
poyunt ut loco hand dimoveantur ; etiamfi omni dtligentia juxta 
methodum dejcriptumper tot urn llorizontem expe> iuntXoJmt femel 
collocata. Adhuc quam ardunm (it, ea rat tone verum eorum locum 
tndagare, fafis fuperq; expert tt* [urn \ jicutvixvideam, an alicui 

circa. 




C 6 > 
circa rejlitutionem Tixarum Vianet aruwq\ adminkulo e§ep$fflnt \ 
in majoribm folic et Hits difiantiis capiendo: In minoribw, Urgi- 
cr y poffe illiquid prsjlari ; fed an Inftrumenta, urirns Spithama 
radio inflruclta, e labor art pojfint muliu exaUius^ qu&m optima qua- 
vis, vulgar es Dioptra* habentia, licet 60 pedum radio elaborate 
nollem adhuc affeverare. Mult a mmq\ in Iheoria videntur cer* 
tijfima, qu£ in praxi fatis longe nonnunquam a vero recedunt. 
Si quis mihicertas obfervationes quarundam dijlantiarum & qui* 
dem Fixarum^ circa Eclipticam & zALquatorcm exiflentium^ il- 
lis ipjis Injlrumentis, Dioptris Telefcopicis injhutfis habitas ex* 
hiberet : (utpote diftantiam Lucid<e V a Palilkio ; Palilicii a Pol- 
luce \ Poliucis a lieguh *, Reguli a Spica W ; Sj?ic<e W <l Boreal* 
finifi. manus Serpent arii 5 Boreal, jinift. manus Serpentarii ab A- 
quila ; AquikaMarcab ; & Marcab ahucida Arietis) vellem 
protimts de rei iilius certitudine ejr meum quale quale judicium fer~ 
re 5 fed antequam eas obfervationes obtineam, judicium fufpendo. 
Interea utiq^fateor ; Ji quis adminknlo minoris cujufdaw inftru- 
menti obfervationes cor for urn C&lefliumperagere poteft, multo pane 
iftum efje feliciorem, variisdecaujls, eo, qui per major a id pr£- 
Jiare allaborat. Rations $ dividendi Instrument a, diver fe qui dem 
mihi probe cognit£ funt ; eafq; etiam in ufum tranfluli ] num 
autemjint eadem quas Cknffimus Dominus Hookius novit, ac 
invenit, me prorfus latet : Stilitnonadverfumefi^ rogo, utpra- 
cipuas communicet^ ego ut meas intelligat rurfus ftudebo. 

Since which time /have not fen t any other defcript ion of 
inftruments, fave that of the manner of making and ufing a- Tube 
for a 60 foot Glafs, which 1 am mach pleas'd to find he makes 
ufe of, and fiiould gladly have communicated any thing fur- 
ther, if I had.not found they were efteemed infignificant. /t 
did much trouble me, /confefs, that /could not prevail with 
him to make ufe of Telefcopical Sights at leaft, fince with lefs 
trouble he would have afforded the World Obfervat ions, and 
a Gatalogue of the Stars, ten times more exact. And / am the 
more forry to find that he hath proceeded tofinifii his Machina 
Coekflis, by inftruments not more accurare then thofeof Itcho, 
and that he dill remains in the fame opinion of Telefcopical 
Sights, and other improvements of inftruments. Forpag.293. 
of this firft Part of his Machina C&leftis, fpeaki'ng concerning 

Sights, 



(7) . 
Sights, he fays, Poffibly fame may wonder that / do not make 
ufe of Telefcopical Sights, fmce they are by fome accounted 
better and more accurate, infomuch that there is one in the 
World hath proceeded fo far , as to fuppofe Telefcopical 
Sights to be ten, twenty, thirty, nay forty times more accurate 
then the common Sights ; and that 'tis poffibleto make- an in- 
ftrument of a Span Radius to do more with Telefcopical Sights, 
then an inftrument of 60 foot with the common Sights. 
'Twould be a thing of much moment could it be done, and not 
to be valued by money, but many things do feem true in the 
Theory, which do not anfwer upon Experience. You may 
perceive by comparing this flender Refutation with his Letter 
before, who he means by the Affertor of Telefcopical Sights. 
But 1 am troubled he fhould think them fo flight as not to 
deferve one tryal in feven years time , efpecially fince by 
explaining the manner of making ufe of them much in the 
fame fenfe with that which /fent him, hefeems to have un- 
derftood enough of the way to have made ufe of it if he would. 
As to his Objection, That the Glatfes are apt to be broke, and 
the Pins or Threads areapt to be bent and broke, there is not 
the lead: colour for it, for they cannot without much labour 
anddefign be broken or put out of order, but if they were, 
it might as wellbefaid, that the Plumb-line of any of his inftru- 
ments may be broken, or his Sights bended, and the like, and 
therefore thofeinftruments were not tobeufed. But thefe 
Objections I fliall not urge agatnft his inftruments, nor a great 
many other / could produce of Jeffer moment, but only this one 
which is very fundamental, and cannot anyways be helped 
but by the help of GiaiTes, and that is, 'Tis impoffible with 
Sights made after Tuho\ or Ueveiius his way, to diftinguifTi 
anydiftance in the Heavens lefsthen half a minute, or thirty 
Seconds,and hardly one of a hundred can diftinguiffc a minute. 

And this being proved, what will become of all the machi- 
nations and contrivances for greater inftruments, to fliew the 
Divifionsof fingle or double Seconds ? May not (ingle minutes, 
nay half minutes, by the help of Diagonal Divifions, be fuffi* 
ciently diftinguiflbed in an inftrument of three foot Radius? 
What need is there then of all the other cumber ? Certainly an v 
one that will but try with the one and the other infrrumenf, 

will 



( s ) 

willfind himfelf able to do as much with an inftrument of three 
foot, as with one of threescore, fmce the eye cannot diftinguifh 
a lefs Angle, at lead none that /have yet met with hitherto. 
Who is there that by his bare eye can diftinguifh any of the Te- 
lefcopkaWpots in the Moon, though fome of them are above a 
minute in Diameter ? As for initance, Who can fee Mount Si- 
»ai 9 fo call'd by Hevelm, which is a bright fpot in a dark 
field, and confequently muft appear near two minutes in Dia- 
meter to the naked eye? Or who can fee the Palus Mareotis, 
or the Lacus mger, which are two dark fpots in light fields, and 
each more then a minute in Diameter i Now if the eye cannot 
diftinguifh a fma'ler object then appears within the angle of 
half a minute, 'tis notpoffib'e to make any obfer vat ion more 
accurate, be the inftrument never fo large* 

Now that any one may prefent) y fatisfie himfelf of the truth 
of what I afiert, concerning thelimited power of the naked eye, 
astothediftinguifhingof Angles ; Let him take a fheet of white 
Paper, and thereon draw two parallel Lines, asOO, and P 
P, in the 28th. Figure, at four or five inches diftance, then 
draw as many other fmail lines between them at right angles to 
them, and parallel one with another, as he thinks convenient, 
as aa, b b, c c, dd, ee, ff, gg, hh, i i, &c. and let 
them be drawn diftant from each other an inch, then let him al- 
ternately blacken or fhadow thefpaces between them, as* be- 
tween a a and bb, between cc and dd, between ee and 
ff, between gg and h h, between ii and kk> between II 
and mm, &c. leaving the other alternately white, then let 
him expofe this Paper againft a Wall open to the light, and if it 
may be fo that the Sun may fhineon it, and removing himfelf 
backwards fur the fpace of 2877 feet, let him try whether he 
can diftinguifh it, and number the dark and light fpaces, and 
if his eyes be fo good that he can. then let him ftill go further 
backward's and backwards from the fame, till he finds his eyes 
unable any longer to diftinguifh thofe Divifions, there let him 
make a (land, and meafure the diftance from his eye to the a- 
forefaid Paper, and try by calculation under what Ang'e each 
of thofe black and white fpaces appears to his e\e, for by that 
mean" it will he manifeft how fmalJ an Angle his eye is capable 
of diftinguifhing, and beyond which it cannot reach: Which 

being 



( 9 ) 
being once known, he hath a Standard, by which he is able to 
iknkthebignefsand exa&nefspf his Inftrutnents,, if; he make 

- ufc of common Sights, beyond which all magnitude and cdi 
oiity is not only ufelefs, but pf much detriment upon many 
accounts. 

This is that Confideration which I could wiHi had occur'd 
both to Xicho Brahe and to Hevelius, efpecialJy to the fetter, 
who hath fo earneftiy endeavoured to ouc-do the former, an4 
for the accomplifhment thereof, feems to have fpared no' 
charge, labour, or endeavour he was able to expend; I hope 
at leafl that this publick notice will for the future engage all 
fuch as fhal! attempt this Work, to be as follicitous about aP- . 
lifting the Eye in thedifeovery of the parts of the ObjeO, as of 
diftinguifliing the Divifions of the Instrument,' for the doing of 
the one without being able to reach the other , will avail 
nothing. 

Thofe therefore that defireor need Ihftruments to make Ob- 
fervations to Seconds, mult take another courfe then any that I 
know yet defcribed. 'Tis true indeed, That Altitudes of the 

- Sun may be taken, with the Sights commonly ufed for that pur- 
pofe, to what accuratenefs is defired, if the Inftrument be large 
enough, becaufethe Image of the Sun being tranfmitted by the 
upper Sight through a (mall round hole, is reprefented within 
a Circle upon the lower Sight, and by means of the eyes ap- 
proaching near that Sight, 'tis poffible by Inftruments large 
enough, to arrive at the accuratenefs of a Second, in Obferva- 
tions made of that kind. And fomewhat of this may be done 
alfo by the Moon,, when very bright and clear, but in all the 
other celefrial Bodies ic has never yet been done. 

But then if we compare even this way with that of Telef- 
copes, ceteris paribus, weflial! find it muchfhort, both as to 
clearnefsanddiftindtnefs, and therefore even here a I fo Tele f. 
copical Sights are to be preferred, as I Hiall fufficientl)> mani- 
fest hereafter more at large, when I come to defcribe my own 
Inftruments for this purpofe ; for I doubt not but to make it 
fufficiently plain, That by the help of an Inftrument I have 
contrived, of three foot Radius, I will be able to make all 
Obfervations whatfoever, ten times more accurate, excepting 
.thofe of the Sun, then any one can make with the kngeit In- 

B ftrumenr, 



C to ) 

ftrument, defcribed either by licho or Hevelim, and to ma- 
nage the fame with a quarter the trouble, clutter, and Appara- 
tus necefTary to either of theirs, and to make the Divifions as 
accurate and fenfible as can bedefired. 

For the doing of which, I will fbew, Firft, How to make 
the Plain of the Inftrument, that it fliaLl not be fubjedl to bend- 
ing or warping, and yet be fo light as to be eafily manageable. 
Secondly, How to make the Divifions on that Inftrument, fo 
as to diftinguifih certainly and exactly to Seconds, without any 
trouble, or wearying the fight. Thirdly, I will ftew how to 
make the Sights of that Inftrument, fo as to diftinguifh the 
parrs oft he Object to Seconds, if need be, even by thofe who 
cannot diftinguifh to Minutes with common Sights, certainly, 
and without fallacy or error. Fourthly, How to make the 
Sights, fo as to fee two Obje&s, though never fo far diftant, 
with one glance of the eye. And Fifthly, I will/ftew how to 
adjuft the Perpendicular, fo as to fet it exa&ly upright and 
plain to a Second, fo that if it meets with a diligent, accurate, 
and experienced Obfervator, it will ferve to make as curious 
Obfervationsas are hitherto defirable. Sixthly, Iwillfliew 
a way how to fix this Inftrument, either for taking Altitudes or 
Azimiths, foas to be manageable with the teaft trouble imagi- 
nable, for Obfervations of that kind, and to be always (ready 
and fixt in any Perpendicular pofture, to whatever Aziroith it 
be apply'd. Seventhly, I will explain an exacl: way for fixing 
the Inftrument, fo as to take the Diftances of any two Stars, 
orceleftial Objedr, and feveral other contrivances of the like 
nature. But of each of thefe hereafter, after I have examin'd 
over the feveral particulars mention'd by Hevelm, in his De- 
fcriptions of the Inftruments and Contrivances made ufe of by 

himfelf. 

To pafs by then his long Preface, and the Difcourfe of In- 
ftruments in general, which he hathpremifed in the firft Chap- 
ter 3 I flhal'I proceed to an examination of thofe Inftruments of 
his own, which he doth more fully and particularly de- 

fcribe. 

The firft of which kind I find to be a Quadrant of Brafs, 
which he defcribes in the fecond Chapter, and begins with 
that firft, as being an Inftrument which he leaft efteem'd, and 

which 



C» ) 

which at length he made no ufe of, though for many ReaionsX 
think of a quantity big enough, to be as good, nay better, then 
any he made ufe of. But of that anon. 

This Brafs Quadrant was of three foot Radius, and fo well 
fitted with crofs Bars, and ftrengthned, that it was not fubjeft 
to warp or bend § it had alfo a convenient Pedeftal, and was 
made eafie to be removed from place to place ; it was fufpend- 
ed by a Cylinder placed on the back-fide, in the Center of 
Gravity of the Quadrant, and could by this means more eafily 
be moved to and fro to take any Altitude, then that way of I*- 
cho% who fixe his Cylinder at the upper corner : But it hath 
this of inconvenience thatT/A's hathnot, namely, That the 
Plumb-Line or Perpendicular will be longer before it fettle, 
and the Inftrument fomewhat more apt to warp. The Sights of 
it are the. fame with that of licho, and indeed the beft of Com- 
mon Sights, now commonly every where made ufe of in Inftru- 
ments of that bignefs, but far inferior to thofe which are made 
ofGlafles, as I fhall afterwards prove. 

The way of Sights which hedefcribes, /tfg.98. for taking 
the Altitude of the Sun, is very good, but yet far inferior to 
one fitted with the Objeft-Glafs ofa Telefcope, though he had 
omitted the Tube, for he might thereby have enlarged the hole 
of the upper Sight to what bignefs he pleafed, and confequent- 
ly have made the image of the Sun as bright as it fhould be 
thought convenient, and that without any manner of Penumbra, 
if the lower Sight were placed at the due difhnce of the Focus 
of that Object-Glafs. And therefore I do wonder at his care- 
fulnefs to inform his Reader aright, for fear he flhould under- 
ftand a Telefcope by the Tube he made ufe of, to keep off the 
adventitious light from the lower Sight, faying, pag. 99, Per 
Tubum mtemmi he ft or nm mteBigofelefcopium altquod lentibus 
inftruftum, fed plane nudum ex char fa conftr u ft umtubulum, as 
if he had fome dread ofmakingufe ofGlaffesinany of his Sights. 
Whether it were, that he fuppofed Glades to have fome hid- 
den, un-intelligible, and myfterious way of reprefenting the 
Object, or whether from their fragility, or from their uncer- 
tain refrafiion , or from a fuppofed impoflibility of fixing 
them to the Sights^ or whether from fome other myfterious 
caufe, which /am not able to think of or imagine, /cannot 

B 2 tell. 



(12 ) 

tell. Surei am, that none of thefe 1 have named, are a$y 
thing at all conaderabie Objections againft their ufe, and J 
have been fo fully fatisfied of the exceeding great ufe, nay ab- 
folute neceftity of them in curious and exact Obfervations, 
that I do afTure him there is not, nor can be any confiderable 
Objection againft them, which cannot eaiily be anfwer'd, nor 
any inconvenience, which cannot with eafe be obviated and 
rectified $ of which i fhall fay more hereafter. 

The Di virions of it were made wholly by himfelf, with ex- 
traordinary labour and curiofity, infomuch that he fays, he 
could not only diftinguifh each minute of a Degree, but almoft 
every quarter of a minute, fufficiently accurate for his Com- 
mon Sights, if he could have only diftinguifhed every half mi- 
nute, and indeed much more then moft mens eyes are able to 
reach. He feems to have been at infinite trouble and pains, to 
perform the Divifions madeby the help of Diagonals, cutting 
parallel Circles, a way made ufe of by Ticho, and now fo com- 
monly known, that I think Ineed not fpend time in the Expli- 
cation thereof 5 only / muft take notice., That*whereas he fup- 
pofes thefe Circles to be equally diftant, he ought to have pla- 
ced their Diftances according to the Proportions of the difTe- 
rences'of the Secants of fome ten minutes,next fucceffively fol- 
lowing one another in fome Degree of the Quadrant, which is 
eafie to determine, from theDiftance of the twoextream or 
bounding Circles $ of which more hereafter. 

Now though the Circles ought not according to the ftrict 
Rules of Geometry, to be equally diftant from each other, as 
Bevelim feems to fuppofe, yet I confefs., unlefs the fpace 
wherein thefe Circles lye be very large, and the parts of a De- 
gree that are to be diftingiiiftit, veryfmall, there is no necefli- 
ty of fo curiouily d i ft ingui firing thofe unequal Diftances, but 
they may ferve well enough for ufe, if they be taken equal, as 
Hevelws fuppofes 9 and indeed much more accurate, then 'tis 
poftible to diftinguifh the Object by the bare eye ; and there- 
fore I fhall not need to infill: upon the further Explication 
thereof, cfpecially becaufe when I come to fliew a more accu- 
rate way of Sights, I fhall alfo fhew a much more accurate way 
of Di virion, then either of thofe two of licho Brahe, or this fa 
down by fkveUm 7 which is much the fame with one of thofe 

which 



C 13 ) 

which was roo years ilnce madeufe of byTnAo, anddefcri- 
bed , and is by him attributed to an Englifli Mathemati- 
cians. 

But becaufe this induitrious and careful Perfon put himfelf 
to the trouble, of making and examining the Divifions himfelf, 
I could heartily have vviiht he had thought upon fome fuch way 
as this, which I here defcribc, and call a Compendium of Dia- 
gonal Divifions, itbeingaway, whereby as |f of the trouble is 
fizved, in performing the manual operation thereof, fo I judg 
it to be much more certain, exacl and plain, then the other way 
of Diagonals. My Reafon for the firft is plain, TheDivifion 
of one Degree ferving for the whole ninety : And my Reafons 
for the fecond are, Fir/t, Becaufe it is much plainer to be di- 
ftinguiflied, then by the help of the edge of a Ruler, lying 
over the Diagonals, one being able to fee but one part of the 
Diagonal. And Secondly, J think it much better then a final! 
fiducial Thread, which is very apt to be bended and broken, 
If it lyes clofe to the Superficies of the Diagonal, and if it lyes 
at a diftance, a skew glance of the eye will muchalter the feem- 
ing interfedion of the Diagonals, which in-thn way are both 
prevented. The way thenin fhort is nothing but this 5 Take 
a thin piece of clear Looking-glafs Plate, well fmoothed and 
polifhed on bothfides, and large enough one way fo cover the 
whole breadth of the Rim of the Quadrant, on which the Dia- 
gonals were to be made, and the other way to cover two or 
three Degrees, ( this I do thebigger, that the fides of the Arm 
may not fhadow or darken the Divifions and numbring^) Sup- 
pofe a a a a in the 29th. Figure, Plate 2. to reprefent faoh 
aPlate, upon this Plate defcribei with great care a Degree of 
the Quadrant you would have divided, and compleat it with 
all its parallel Circles and Diagonals, as you would have done 
any one Degree upon the Quadrant, and if the Rim of the Qua- 
drant be very broad in proportion to its Radius, you may by 
the Table of natural Secants or Tangents, fet the parallels- at 
their due Diflances, but if the Rim be narrow, 'twill be fuffi- 
ciently accurate to make their Diftances equal. Thefe Divifi- 
ons muft be done with CompafTes, pointed wirhfmallDiamanc 
Points, in the manner of rhofe wherewith Glafiers cut their 
Glafs, The Glafs being thus divided ,and lined, number the 

Diagonal^ 



( 14 ) 

i&gftnals, and place it in the Frame of the Ruler, with the 
lined fide next the Quadrant, fo that moving it to and fro, the 
fide of theGlafsmay immediately touch theBrafsRim of the 
Quadrant. This Brafs Rim muft be divided into 90 equal 
parts or Degrees, and at each Divifion ftraight Lines drawn 
from the Circumference towards the Center,the whole breadth 
of the Limb, ( at leaft as much as is made ufe of for the Glafs- 
Plate, for the breadth of the Diagonals) the Frame to carry 
this Plate is a convenient Cavity, left in the moveable Arm of 
the Quadrant, the whole manner of which will be better under- 
flood by the Delineation thereof, to which I fball therefore 
refer the Reader. TheDifrances of the parallel Circles if un- 
equal, may beeafilyfet down true, according to the numbers 
of natural Tangents or Secants, with a pair of Compares, con* 
trived like Beam-Corn pafTes, but having its Points to be fct at 
any diftance, defired by the help of a Screw, moving upon one 
fide of the Beam, which I may have occafion to defcribe elfe- 
where more properly, and therefore will hereomit it. 

Next, If this way had not plea-fed,. I could have wifhed he 
had known this following, which is altogether as eafie, and as 
Geometrically true, which I have contrived, and have made 
fmall Inftruments thereby to fliew very miuute Divifions, very 
eafily and very plainly. I ftrike then upon the Limb of the 
Quadrant I would divide, being firfiraade exceeding fmooth 
and plain, a Circuie very fine, and as lightly as poffibly I can, 
fo it be but difcernable, and by the help of a very large Qua- 
drantal Dividing Plate of ten foot Radius, I divide the faid 
Quadrant in the faint Circle above- mentioned, into 90 parts 
or Degrees, then by a peculiar contrivance of a very curious 
Point that fthkes with a Spring, which I defcribe in another 
Difcourfe, the faid Degrees are marked upon the Plate by cu- 
rious finall, round and deep holes, thefe are by another Line 
without it, which is divided and figured the Common way, 
diftinguiflied and numbred by Figures, according to the Com- 
mon manner. Then for the fub- Divifions^ I make a final I 
Hold-faft by a Screw, which is fixed on to the moveable Arm 
of the Quadrant, this ferves to hold the end of a Diagonal 
Hair, the other end of which is ftrain'd over the Supplementary 
Degree, till it Jyethdire&ly over fome prickt-Hole of the curi- 
ous 



( is ) 

ous Divifions, on the Limb of the Quadrant, this gives me the 
fub-Divifions of the Quadrant, to what accuratenefs I defire. 
The Supplementary Degree is a Degree of a very large Circle, 
put on upon a fmall Rule, fixed on to the (ide of the moveable 
Arm, whofe Magnitude and Diftance is found by this Propor- 
tion, as the Diftance between the end of the fmall Hold-faft and 
the pointed Circle, is to the Radius of that Circle, fomake 
the Diftance between the faid End and the Supplementary Cir- 
cle to the Radius of that Circle. This will be more plain by 
a Scheme. 

Letaaa in 'the 30th. Figure reprefent a Quadrant, b.b'b 
a very fine Circle, ftruck on the Limb of the Quadrant, from 
the Center 1, which by a large Quadrant of ro foot Radius, 
I divide into Degrees, and by a fpringing Point ftrike fo many 
fmall Points, and number them to 90. beginning at m, and 
nurabring towards i. Let d d reprefent the moveable Arm, 
c c the hold-faft, fixed upon the fide of that Arm, which by a 
fmall Screw pincheth and holds faft a very fine Hair at k, ee 
the fmall Ruler fixed at right Angles, with the Line 1 k f, in 
this Line (through the Points 1 and k) I take a Point, as f,and 
through f I ftrike a part of a Circle fg, whofe Center is 
fomewhereintheLine fkl produced, which I find by refolv* 
ing this Proportion, as k i is to li, fo will k f be to the Ra- 
dius of the Supplementary Circle fg, which will fall Come- 
where in f k 1 produced, towards 1, then take a Degree of 
that Circle, which will extend from f to g, and divide it in- 
to as minute Divifions as are necelTary, and number them from 
f to g* Now to find what Angle the Sight dd maketh with 
the Sight mm, I ftrain the Hair h k, till I find it lye over the 
next Divifion Point towards the right hand, and obferve in 
the Ruler e e, what part of a Degree is there marked, aod on 
the Circle bbb, what Degree is marked, the fum of both 
which gives merthetrue Meafure of the Angle d d 1 m. But 
this only by the By, and I will not now further enlarge on the 
Explication thereof, defigning it for another Difcourfe, 
where 1 fhall defcribe various. Mechanical and Practical ways, 
of accurately dividing Lines, into any affignable number of 
equal or proportional parts. 

To proceed then where I left off, to the examination of 

tfee 



( i6 ) 

rhe Inftruments of Heveliw, I find that together with the Brafs 
Quadrant I was fpeaking of, hedefcribes two Contrivances 
about it 3 Thefirftis, How to fet it prefently to an upright, 
without the trouble of turning the Screws in the Pedeifed* 
which is plain enough, and fo much the better ; but it hath this 
of inconvenience, that it muft be altered for every Azimith, 
which is a very great one, and which by another, way altoge- 
ther as eafie and plain, may be avoided ; of which more here- 
after. 

Another Contrivance about this Mrument, is a fmall Screw, 
for moving it and keeping it fteady in anypotfure in the fame 
Azimith, which is convenient enough, but will not perform 
what he afterwards fuppofes it capable of, as 2 ftall afterwards 
fhew.- 

The fecond Inftrumenr, which in the third Chapter, fag. 
102,103, &c. 108. hedefcribes, is a Sextant of Brafs, of 
three foot Radius, carefully made, and divided with the fame 
care and after the fame way as the former. The Sights alfo are' 
much the fame, only whereas in the Quadrant he makes ufe of 
a Plate, with parallel edges for the Sight that is at the center, 
and furtheft from the eye ; in this he makes ufe of a Cylinder, 
which way alfo Ticho made ufe of 1 ©o years ago, and hath been 
ever fince made ufe of. The other Sights next the eye are the 
fame with the former : There is nothing lingular in the Vede- 
ftal, nor in the Ball and Socket, only 'tis fomewhat bigger 
then ordinary. His way of moving and fixing the Rule of it is 
convenient enough, and the fame with his /nitrutuent for moving 
and fixing his Quadrant, but 'tis not capable of performing 
what he promifethfor.it* 

The third /nftrumeht, which in %fourth Chapter he de- 
fcribes, is a Sextant of Iron, of fouWoot Radius, to be ma- 
naged only by one Obfervator, by putting the Center .next 
the eye. The whole /nftrument is iittle differing from the 
former, fave only that the Cylinder at the Center which is here 
next theeye, is cover'd with another hollow Cylinder, which 
is voluble and convertible about the former, and carries two 
finall Slits for the Sights, which performed! the fame as the 
other Sights, but nothing more, and as the Author himfelf af- 
firms, is notfo accurate for ufe as the other Sextant, where 

there 



( «7 ) 

there are two Gbfervators, and therefore was feldom made ufe 
of by him. But I fliall anon fhew a way by which one Obfer- 
vator alone fliall be able to take any Diftance to a Semicircle 
with much more accuratenefs and conveniency then any two 
Gbfervators can ; and therefore will be an Inftrument of the 
bed ufe for Agronomical and Nautical affairs,for the perfecting 
bothwhichldefignit. 

The fourth Inftrument, which in the fifth Chapter, from pagl 
1 i4,e?F. to 1 23. he defcribes,is a Quadrant of fix foot Radius, 
whofe Frame was all made of dry Oak , but the Limb,Sights, 
Sockets,^, were made of Brafs, divided fo as to fee every 
quarter of a Minute diftin&ly, the Sights the fame as in the fir It 
Quadrant,and the way of fufpending it not much differing, fave 
vfiDnly, whereas in the former the Pedeltal was moveable, in this 
it is fixt, which is much better. And the Inftrument is kspt in 
•an tALquilibvium, by the help of eounterpoifes hung at the end 
of aftring, andcaftovera Pully, as is more vifible by his De- 
fcription. But this (as all other wooden Initruments doj Jhe 
found to flirink and warp, and confequently to lofeits ex/ct- 
nefs, and therefore he made little or nolife thereof, but laid it 
afide, and made himfelf better of Brafs, 
. The fifth Inftrument defcribed in the fixth Chapter , from 
j>ag. 123. to 132. is a Sextant of Wood of fix foot Radius.made 
in all particulars like the former Sextant of Brafs of three foot; 
nor has it any other contrivance about it considerable, fave on- 
ly a reft made to flip up and down for the Obferva'ors to reft 
their Elbows upon. . But this Inftrument alfo he found to be 
vitiated by the flirinking arid warping of the Wood, and there- 
fore he laid that by aifo, and feldom made ufe of it. 

The fixth Inftrument is a large Octant of Wood of eight foot 
Radius ; this is made exactly according to the Form of X/Ws 
Octant, and ferves for taking any Diftance not exceeding 45 
degrees. The Sights near the eye are made exactly as the former, 
but moveable, fo as to flip upon the Limbs of the Octant^ the 
Divifions of it are performed by Diagonals as before, and gives 
a greater nicenefs of Divifion then the Eye is capableqf diftin- 
guifliingin the Object, and therefore of little ufe. 

And thus far the Author proceeded in Ticho's way. 
But finding thefe Inftruments which were made for the moft 

C . part 



C 18 ) 

part of Wood to he fubjeft to faileur, he afpired to get better 
Inftruments made all of Brafs or Iron, and wholly laid afide 
the reft as altogether ufelefs. And I cannot but very much ap- 
prove of his Judgment in fo doing, fur certainly ceteris paribus 
Inftruments, well made of Brafs or Iron 3 are much to be pre* 
ferred before the beft of Wood. But yet neither are all man- 
ner of Wooden Jnftruments tobereje&ed; nor are all forts of 
Metalline Inftruments free from error, though 'tis con fefled, if 
they be made and ufed with skill, they fufler not any confide- 
rable or fenfible variation. Firft, I fay, Wooden Inftruments 
may be To eontriv'd as very near to equalize thofe of Metal, the 
joynts and Plates for Divjfioris only being made of Metal, they 
being very eafie to be rectified before, and examined after eve- 
ry time of ufing. Such a one was contrived by Sir Chrijiophe^ 
Wren, being two fquare Wooden Tubes or Telefcopes, joyn'd 
together at the end next the Objecl by a Joynt of Brafs, and the 
Ang 1 e made by the opening of them, meafured by a ftraight 
Rule equal to half the Radius,divided by Diagonals into 5000 
equal parts, which will by the help of a Table 0/ natural Signs 
or Subtenfes, fliew th& parts in Degrees, Minutes,and Seconds, 
of which I think /acquainted Hevelwfome years fince r Next 
Brafs and Metalline Inftruments, if they be not very carefully 
fortified a gainft it, are more apt to bend then even thofe of 
Wood. And thebeft way I have found to fecure them true and 
plain in all poftures, is to Jay them on a Table or Frame of 
Wood, well fortified underneath againft bending , and by the 
help of final! Screws in feveral parts of the Inftrument 10 ad- 
juft it upon that Frame k the whole Table and Quadrant being 
focounterpois'd, as to be eafily moveable and fixe in any po 
fture. But Bevelim is pleas'd, as I faid before, wholly to lay 
afide all manner of Wooden Inftruments as ufelefs, and to indea- 
vour the obtaining of Inftruments of Brafs or Iron.. AW (fayes 
he pag» ig6. ) cum longa experientia probe tandem didicerim, 
multo fecurius ejfe ex [elide ptorfus mttahoobtinere infir amenta , 
turn quo major a ejr ampliora eo ejfe accuratiora & abfoluticra^ ad- 
h&c prior ibus admodum tichonhum am^ructis .plurima deejfe qui- 
bus ditari merito deberent , & quod iijdem de caufis ommm ne^ 
seffumfit^ ut parte corrigerentur ejr meliorentur , tarn qua eornm 
materiam fruEtur&rn commottontm facilitandam divifionem quam 

alia, 



C 19 ) 

alia diver fa fubftdia & adminicular fie *ptiu4,txquifitiusMoMp- 
titts .mmoriquelabore^c. actemporis di/pendio foment Afiris ex- 
font obfervationefque pragu Idcirco omnem cur am atque #pr am 
fro tend ingenii metfaculutumque me arum modulo a Deo concetto- 
( reliqua juhlimioribw ingeniu atque ampliori for tuna Fins, five 
pftentati nojlrtrelinquens*) adhibuh\ quo minor a y tarn lignea u- 
niverja ab Apis plane removerem, atque in ejus locum ex pro 
filidbque metallo, organamihicompararem: & quidem eju/modi, 
qu£ infigm amplitudine ejfent conjpicua, fimuleommoditate reoen- 
di, [imul aliquant accuratioribmadhuc divifionibm, ad putt [ub- 
tiliores obfervationes obtinendas gauderent. His Reafoaiog in- 
* deed is very good, that fince he' had from much and long expe- 
rience learn'd, that Inftruments of Wood after Ticho's* manner, 
were not to be trufted to by reafon of their warping -and 
prinking, and confequemly that Inftruments of folid Metall 
were much to be preferred before them, and alfo that the lar- 
ger the Inftruments were, the more exactly they could be made 
and divided,and that the more eafie they were to be moved, and 
the more fteddy and fure they were to be fixt in any pofldon, 
the more convenient they were for ufe, he had therefore rejecV 
ed all thofe Inftruments which he had made afcer Tkho's way 5 
and had indeavoured to procure for his own nfe iuch as were 
compiear, both for their matter and form, having caufed them 
to be madeof Mettal that which could not be fubjeel to the 
inconvenience of warping, fwelling, or fhrinking, with the 
variety of Weather, or length of Time: And likewifeof fuch 
a bignefs as was capable of receiving more nice and curious 
Divifions ; and in the dividing them had found fuch contrivan- 
ces , and ufed fuch diligence, that they were more tjien ordi- 
narily true and exad. As far as he has gone on wi t h thefe De- 
figns, he fcems to have been even profufc in his expences, and- 
exceeding bountiful of his own care, labour, and diligence; 
but I could have wifh'd heartily that it had been fome other 
way imp oyU Thofe Inftruments which he chiefly laboured 
toper: he profeftes to be Qnadrams, Setfants,and Oclants, 
after lichoi manner, rejecting all O'her Mriimwsof whatfoe- 
j^er Figures, whether -Radii, Apolabs , Zodiacal or zMquino* 
Ui'al Kings, Farallatfical Inpuments or Hoops, as more rroti- 
blefome, and lefs accurate. But whether he hath in this his 

C 2 choir : 



( 20 ) 

choice been rightly advifed, I fball hereafter have moreocca 
(ion to examine when 1 come to defcribe an Apparatus of In- 
ilruments neceiTary for fuch a one as defigns to promote and 
perfect the knowledge of the Cceleflial Eodies and their mo- 
tions $ Wherein I fhall fnew that of fome Inftruments rejected 
by him, there is a ufe abfolutely neceiTary. 

The Inftruments therefore that he begins with are three final 1 
Quadrants of Brafs *, the firft of two foot, the fecond of eigh- 
teen inches, and the third of one foot Radius. Each of thefe 
Inftruments, he fayes, were made fomewhat larger then common 
Quadrants, to wit, of an arch of i io degrees 5 which is to no 
other end, but only in order to (Lew the fubdivifions of each 
degree of the Quadrant, by the help of a new invented Per- 
pendicular of Brafs wherewith each of them was furnifht. This 
Invention is by him highly extoll'd for mod: excellent and ufe- 
full 5 and to that end is made ufeof for the divifion of all his 
other Inftruments, both great and fmall. Hear what he fayes 
of it ; ^uifiunqtte hujus rei (to w 7 it, the new way of fubdivi- 
ding the degrees of the Quadrant) primus fuerit repertory [Mi- 
mes Profetfo cogitationes exercuitjjoc ip[o ad congruent em effettum 
deducendo, & inter fr&fkantijjlma invent a meritiffim'o refertur % 
quod etiam minora Infirumenta remotis omnibus tranpverfalibus 
Lineis, in Jingu la minut a eorumque particular minim as [ubdividi 
liceat. He feems indeed both. here, and el fe where in many o- 
ther places of his Book to be highly potTeft with admiration 
of thefublimity, fubtilty, andextream ufefulnefs of this in- 
vention, and feems very much concern'd that the Author there- 
of fhould not certainly be known, but dares not father it upon 
any one pofitively. He fayes that one Benedictus Hedrcm in a 
Work of his which he publifhed Anno 1643. abour the new 
and accurate Structure of the Geometrical Aftro'ab, defcribcs 
it', but he gathers that he was not the Inventor himfelf, but ra- 
ther that he got both this Invention and the whole Quadrant, 
which he defcribes out of the Obfervatory,or rather Reposito- 
ry of Ticho Brahes Inftruments, for that it feems Ticbo was the 
Inventor of this way of divifion ; and yet , as I noted before, 
he prefer'd the way by Diagonals much before it, whatever 
Reafon Hevelius had to be of a contrary judgment. What this 
way is I fhall by and by explain. But in the mean time I am 

lorry 



( 21 ) ' 

forry to find Hevelius joyning with Hedreus in the Opinion or- 
Demonftration, as Hevelius calls it, that the Sub-divifions by 
Diagonals is not capable of a Geometrical demon(tration,efpe- 
cialiy in letter Inftruments, which have need of many Circles. 
I confefs 1 underfiand not their meaning nor reafonk)g,nor why 
icfhouldbelefsdemonftrable in lefier then in greater Inftru- 
ments ; fince 'tis very eafily demonftrable both in greater and 
leffer Internments, and as Geometrical as any other way of Di- 
vifion whatfoever : the Diagonal Line being alwayes a piece of 
a Tangent Line, that is to fay, the fpaces between the Parallel 
Circles upon the Diagonals are alwayes to be in proportion to 
the difference of fome Tangent Lines, and the different difta'nce 
of thofe Circles from the Center are alway in proportion of 
fome Secants : And the way of finding what ihofe Tangents or 
Secants are, and confequently what muft be thofe Diftances of 
the Parallel Circles I mentioned briefly before, and fball now 
more fully demonftrate. From which I will make it evident, 
that the Theory was not as Hedreus and Hevelius have fsippo- 
fed, uncapable of Calculation or Mechanical Demonftra- 
tion. 

But firft give me leave to fliew you what way Tieho Brahe 
made ufe of io demon (rrate, or ra herto find out the true An- 
gle unto each-equal Diftance , which I find fet down at the lat- 
ter end of hi< Mechanic ks, as a Supplement to the reft. Di- 
vi(lonis punc~la habentistranfver [alia modus talis eji , #£34 ex- 
primitfigura in qua jinguU denominate, per Lincolas in decern in- 
ter fiitia aqualia difcriminatum punBis not at a funt, Jicqwe regula 
fiducice quodcunque horum inter obfervandum tranfiens if Cum mi- 
nutumgradus, quid quareb at ur pr omit aut aliquot am ejuspartem, 
pout ab hoc vcl illopuncto remove ri difcernitur* Ut vero hoc e~ 
tiam demon ftratum h'tcaddam ob fciolos forte quofdam qui ea qit£ non 
fath cafiunt carpuntfic habe. 

In Figura 34. Sit A centrum Injlrumenti ejufque Semidiami- 
ter A O, affumttur aurem O I, J*articula in qua divifio ifia per li- 
ne as tranfverfasjit ea proportione qtu eji r ad 48. qualis in me is 
Infirumentis utplurimum ufurpaiur. Cumque A \pomtur partiam 
1 0000000000. integri canonk major it Rhetici } erit earundem 1 
208333333 utpote pars quadr age fima oSiava radii Arcm IE fit 
2o\& I V. i*> .horum firnts 29088779 Y LSinas&utemfecundus 

eorundem 



• f 22 ) 

■ccnnkm 42308. V Y* quiadditm NVquod<epale eft Q I facte 
N Y 2083 7564 r. Intnanguloigitur NYI ^ Y rellangulo nota 
junt duo Later a N Y <£; Y I. quare datur bafis I N 2 10396208. 
#/& tw» <wg»/0 N T I Y 820. 3'. r o". 47". euiadditm YIA 89 . 50'. 
*««/&# N I A; 17 1 9 - 53'. r 0^.47'", Bafis vero N I ^ trUngulo 
recidngulo N V I dividatur in decern fortes aquales utconveniant 
unimmuto 21039621 reprefentateperl B* Moxfte intriangulo 
oblifier^otdo BIA* danturj duollateralB & Ih.radim.unacuman- 
guk BI A,^i /i<?« <?/? ^^ Nf A 1 7 r Q . 5 3'. r o". 47'". ^r/W /v/>*rta 
quire innotejcitangulm 1AB i\\'\i'\quitantummodo\ , .efie debe- 
rely it a tit major ft faltem 1 ". 7*". differentia fane infenfibili: fi- 
milker fi F \ ajjumatur ,nov en particular um erunt ^189356587 
habtMmtfque. rurfes tr Unguium VIMn quo dantur duo later a FI 
modo diclum una cum radio I A. e£- ^£0/0 F I A ah iijdem compre- 
hend velut antea exurgitque angulm 1 A F 9'. 1". & ". quidebebat 
efe 9' *jw#* deficiente in ultimo minuto t» N. i'[. 6'". IVr<? /tf 
fira medium idem, tentetur quod nmc apud extremitates fecimm 
wveniuntur eadem qua antea frimo Angulus I AH 5 \ 3",, 6'". 
abundans 3". 6'". &wW<> ^0/0* N A H 4'. 56". $$"'. deficiens 
3". 5'". jP^/ //^#<f ^W maxima differentia, five adjecliva , 
y?x^ abktiva in hac pragmatia proveniat minimum quid ultra 3". 
qnamfubtilitatem vifm acumen dijcernere in quocunque tandem 
trftrumento nulhientts fuftinet, qu<e etiam per je otto fa eft, quare 
fruftra nodum in Scirpo qu£runtfiqui banc noftramfatis accuratam 
diftributionis formam cavillari pmfumnnt. By which 'tis evident 
that Ticho underitood an inequality, and what it was, and that 
11 was infenfible, and fo not to be regarded. Now 'tis to me 
very wonderful indeed that Ticho having thought of a way of 
calculating this inequality, flhouldnot thinkof an eafie expe- 
dient of reforming it by putting the Parallel Circles at unequal, 
but their due proportionate diftances. And 'tis much more 
ftrange that Uevelim fhouid ft ill affirm it to be a way not Geo- 
metrical : For to any one that confiders^his proportion, the 
inclination of a Diagonal Line being given to find the true di- 
/lances of the Parallel Circles that fhall divide any afllgnable 
pare thereof in any proportion afllgned: Nothing can be more 
eafle: and for more expedition ufe may be made of the Table 
of Natural Tangents which is ready calculated to hand. For 
infrance: Let BCreprefent a Diagonal Line fubtending an an-. 

gul 



03 ) 

gul of ro'.at the Center A. : , produce thefaid Line BC to F,and 
let fall a Perpendicular, from the Center A to E. Suppofe 
then the Angle at B to, be one Degree, then is B E ihe Tan- 
gent of 89°. to the Radius A E. and EC is the Tangent of 
&8. 50'. and the differences between the Tangents of 88. 5c 



j 



88,51. 88, .52. 88, 5-3. 88,54. 88, 55. 88,56, 88,57, 
88, $8. 88,59. and 89. gives the Diftances of the feveral Cir- 
cles, C» 1 2 3 4 5 6 7 8 9 B. deli red. 

Since the Reading of this Left u re, Dr. Wallis hath alfo ce- 
fcribed another way of finding thefe Diftances, which he hath 
communicated in a Letter to Hevetius, and I have prevailed 
with the faid Doftor to permit it to be here printed, being very 
ingenious and accurate, aad proceeding by a differing me- 
thod. 

Dr. Wallis his Letter to Hevelws. 

~~Q\ED & eft cur commum omnium Liter at or urn nomine re'bm 
\^)prsfertim cdlicis addiBorum reddam gratias turn obimmen- 
fos in unto apparatu fumptos eregatosjam pratiofum conquirendo fu- 
pettetfilem Aftronomicam, graphice hie defcriptam, turn oh inde- 
feffos labores, infomnes noffes diefq$ occupatifjtmos cceleftis acqui- 
re ndis obfervatiombus imp en fos ; %uarum vim ingentem, Ike [du- 
rum fupra Mir urn & margaritm pr#tiofum erudito orbi jam ante de~ 
deris, plura daturus indies v verum non eft ut fperem me verbis 
square po$e tua merit a, qui ex privatopenu fumptos plane Rcgi- 
os erogafti-^ onufqs [ufcepifti non inf elicit er, Herculeis Humern 
(ne Atlanteis dicam) formidandum. 

Operis partem maximam jam evolvi, miratus inibi tanta molts 
Inftrumentorum ingeniofiffimum regimen, & fnbtilijjimam divi- 
Jlonum adminiftrationem, cum pari diligentia con'pnebam in Re- 
gulls ejr Dilptris folicite curandis, & quidemjihoc deejfet reliqum 
in cajfum c<ederet labor \ quippe exiguut & vix evitabilis in Re- 
gulis ant Dioptris error ', totum Inftrumentumvitiaret, omnefq; in- 
ficeret obfervationes, fedjingulisimmorari non licet, unumtamen 
eft quod attingam breviter^nempe diviftones per Line a* Diagona- 
ls ^ circulos in limbo concentricos oblique [ecantes t Ham dhi- 
dendi methodumjam diureceptam, ipfe refines & quidemmerito, 
circulosq) hos concentricos aqualibus intervallis disjunclos ' habes, 
quod quamvis in exiguorum aut etum.mediocrium Inftrumentorum 



C 24) 

llmhh htwibm dlqnU erroris poffit inducere in tuts tamen tant<e 
ampUtudims Inflrumentis cum limbis exigU£ latitudinis ( quod & 
tnrcchmones) nihil quicquam erit difcriminis quodin fenfus oc- 
currere poffit. Hac tamen occafine libet hie fubjicere, quod ea de 
re jam olim {circa A. 1650, aut 1 6 5 1 .) meditatusfum, atq$ apud 
aaverfaria me a nunc referio : nempefi quis vellet minoris Infirm 
me dit limbum latiorem Lineis Diagonalibm fie dividere^ ambus 
intervallis oporteat concentricos illos circulos difponere ut angulos 
invtcem <cquales defignarent M<e cum tranverfali interfecJiones 
cdculo Trigonometrico determiner e. 

Dhifio arcus in limbo quadrant is ( aliusvt ejufmodi Jnftrtt* 
me nti) per circulos concentricos & re clam Diagonalem^ Jit la- 
titudo limbi (RL-) L, Radius circuit intimi (AR=) R, extim* 
(AZ=AL~) L+R=Z continent es angul 'urn (RAZ=) A. dividen- 
ds in partes quot libet equates (quarum numerus n) reclis a,b,c, 
<&c. (quarum longitude qu&ritur ) facientibus ad RZ diagonalem, 
angulus *, /3, y , <T, &c. adeoque angulus RA a = £- A, RA b = -£ 
A. R A c=r \ A, &c. fitque ARZ=0 & AZR=* V* Datis ergo 
crucibus R, Z cum angtllo contento A. (adeoque r eli quorum fumma 
O t V) inveniuntur reliquiO obtufus V accutus^) NamTL* R. 
Z-R:: Ita tangens 211. tangentem 2zl & £_+Zt<?_ v = 0. 
deinde cognitis angulis O&f^ (tdevque reliquo a) cum trajec7o 

latere R babetur latus a. nempefinz* R w finus O. a. & pari 
(OiA.^Cb 

mo do ex cognitis *\ o ■* A . ("** / d 

Praxis fit R= 1. L-o, 2. Z=r 5 2. A=io'. dig* Of Vcs 
179°. 50'. ^11 =89°. 55'. /»wZ + R = 2-, ii. Z-R =0,2. :: 
5LtY= 687, 5488683.62, 5044427= tang.<±ll cut refpondet 
angulus 89 . 5'. o". 17'". pw. J&g* ^ + °_L v = o = 179°' 
o'. o'\ 1 Y'\ fere cujus finus o, 01 745 11. #*»*/* idem qui finus 

Deinde fecandusfit A in 10 pxrtes quarum qmlibet fit i'.qu<e- 
runtur /^/tar a,b,c,d,e,f,g,fc,i, 'nempe t . 

Sin* 



(2* ) 

Sin.&Co & 5S ; 5p"43 w ')o.ci7ido3. RvainSi* 0=30.0174511. Loi^^a. £*' 
Sin.$(o 5r.59.43. )o.p}6$6-94. R—i:: <?«* 0=0.0174511. .i.03448=*b. I 754 
S**.yfo 5^5^43- Jo.oid578o.J 0.01745 11 (1.05 2 ^^c.*™ 

$in.£(o 55-5£43» J0.0K52877.J 0.01745 iiCi.07i44=d. ° 

Sin.t(o 5i'5P-i3- J°-oi$p96p.) o.cr^iit'i.opopi^e. '^7 

Sin.*(o 53.5p.43. Jd.oitfoSo.) 0.0174511(1. niio=£ J ^ 

£«f.wfo 52.5p.43. 30.0154152.3 o.oi745iiCi.i320^=g.^^ 

S/*.afo5r,5943.>.oi5i3430 0.0174511(^1.15383=11.^ * 

Sin.t(o 50.5p.43. ^0.0-143335.) 0.01745 11(^1.17647=1. ?^ 

i.20boo=2» 

Praxis altera fit R = r. L==o,t..Z=i,-i. A=io". ^£0 ~= 
i ?9j 5°« 2 ~=§9'- 55'- *#jw tangens 687, 5488693, ^- 2, r„ 
0,1:: 687, 5488693. 32, 74042231= ta#£. 18 9 . 15'. 1^ 
Sff^r ^^t°-^==0=i 7 SVio'. Pf|V T ^ cujus comply 
mentumad femicirculum i\^ '.58". 2 r "f .cujusfinuso i o^i9^2p 

*rg° .; - .*' 

, ,*„. /'i.ooooo—R 

S^A=i.48 # 58.2i)~3i692o)3r9827\i.oo9i8=a 9Ib !6 
Si#.££i.47.5©.2^)— 3140 13)319827 (i*oi852=b934 * 7 

S , ^.>(i'46.58.2p=:3iiio3)3i982 7 fi.o28o3=c 951 * 9 
Si«.j<i.4S.58.2J)=3c>8i98)3i98a7 ( I -°3773-^o 19 
S*#.e (1.44.58.2^ )=3o529o)3i9827 (1.04762=^ 9 9 

,302343) Ci.oS769=f l ^°7^ 
299475) (i«o679*=g °'£" 

293660) (1,08911=1 l ^| 
290752) (r.ibooo=k~ 

HaUentts adverfaria, ubi duos cafes expendimus, nempecum 
latitude limbi ponetur pars quint a & pars decima Radii brevioris, 
& angulus dividendus 1 o minuta prima t ant a fere ei*e<j8«* 3 quan- 
tum feret vulgaris canon trigonometricus: & quidem ultima uni- 
tasin ambiguo eft \; nuncjujfa major nunc" jufto minor. Radium 
autem ( ut ego foleo ) facio L ( non ut pier umq\ fit 10000006.) 
-quo omnes multiplication es ' & Divifiones per Radium facie nda. 
pr£cidantur : Adeoq) finus habeo fro partibm decimilibus, quibus 
staq; cum opus efl^cifhrasfr&mittoquo de unius integri loco 
conflet. D Similt 



( %i ) 

Simili proceffu utendum erit mutatis mutandis Ji latitude limit 
fumatur in al?4 quavis pvprtione ad Radii longitudinem. Sed 
commodius erit ( *d vttandam moleftiam toties qumendi partem 
proportionalem) ut fumatur angums O commoda magnitudinis 
(juftis minutis frimis deter minanda abfq; annexis fectmdis terti- 
ifve) atq\it& queer atur Radii maximi Z longitudo, eodemmodo 
qu£ Reliquoruma 9 b ? c,e^- put a Ji in fraxifofteriorifumptout 
priusR^i & angub A=i o' fumatur angulus Onon qui iliic prodit 
178, i "©', 1 ", 5 7 "' \ fed potius 178. 1 o'. cujus complement urn ad 
duos Re If os eJiu.$Q'. hujus Jinus in ipfo camne habetur 0,0319922 
& reliquorum item A^c^y^ejrc^ftnusfimiliter ibidem habebuntur, 
utuna tantum divijione opus Jit pro Jingulis exhibendis ipfaque Ra- 
dii Z Longitudo habetur non quidem precifeut frius , 1, 1 ; fed 
proxima {qua itaque fumenda erif) 109996 nempe„ 

(l*OQOOO=R ajy.ij 

SV^*(=i.49)=3i7°i5)5 I 9922(i.oo9i7=a 9 ~, |8 

C ^i. 4 8)=3i 4 io8)3i9922 i.oi8si=b £^ 

&c. -311200) 1.02803=0 6 9 

308293) r.o3772=d 8Sl9 

305385) x.o4 7 6o=e o 

30247S) I -°|767-r io27 . 2o 

296662; ..1.07841=11^ • " 

293755) 1.08908=1 ioS8b 

S/X*( = ;T.4o)-29o847) 319922 1.09996— k =z 

fmtiiteromninoresfucceditfifumptisRadiis RL cumangulo A 
qu£r&mm V ejrRadio\intermedio,s, aut fumpto Radio L cum an- 
giitis AV qu&rantisr R & Radii intermedin 

Verumfi limbi Utitudoftt Radii non nifipars trigeffima quadra* 
geffima, quinquageffima aut adhuc minor 9 at q; angulus divide ndus 
non quidem 10 minuta prima fed totidemjecunda,aut minor adhuc ', 
fnbtilior res eft quam ut canon vulgaris Trigonometricus hie adhibe- 
atur ; ejr qu<e omnem fenfum fugit, ipfiq\ circuli concentrici di- 
jlantits aqualibus quantum fenfu poffumus diflinguere invicem dif- 
jun ffi : quippe unius pollucis pars willejima nedum decies aut cent i- 
es millefima minor eft difirepantia quam ut fen fu per dpi pojjit. 
Sed nimius fum in re levifelhemitaq\ exeunt em annum tjbi corn- 
precatus long* fequentiumferie contrivandum, valerejubeo. 

But 



C 27 ) 

But to proceed In the next place I think it willjbe fuffiic* 
cntly plain, to any one Chat fhall try both the ways, thai the Di vi- 
rions are by Diagonals much eafier diftinguiffied by the eye, then 
by this way fo applauded by Hevelius, and therefore I cannot 
choofe but conclude with Hevelius, ( pag. 140, J though to a 
quite differing end and fenfe : Sunt igitnr ftlendidiffhnx tantum 
fyecnlationes mentisq; ide<e quwunf; de Nonianis vel Hedrianis 
Divifionibusproferuntur. But becaufe perhaps there may be 
feveral perfons chat have not yet perufed this Book of Heveli- 
us, nor that of Benedicts Hedreus, printed in 1643. nor Ti- 
chos Meehanicks, of a much longer (tending, and thence may 
perhaps not fo well underftand^what this way of fub-dividing 
is; give me leave a little to explicate it, and ftew you plain! v 
what it is. 

The way then as it is defcribed by Ticho Brake % and afcri~ 
bed by him to Petrus Nonius, that excellent Spanifh Mathe- 
matician, whopubliflitit in his learned Book, de Crepufculis, 
fuppofing it alfo to have been heretofore ufed by Ptotomy, but(as 
ticho is of opinion) without much reaibn, is this; tttducan* 
tut intra extremum quadrantem alii minor esnumero 44. fuccefft- 
ve fefe comitantes, quorum extimus in ^89. fequensinSS. tertius 
foZj. dr fie deinceps donee ad ultimum & intimum perventum 
fueritqui 46* fortunes habebit. To which Defcription pub- 
lifted in his Mechanica, haadds in the fecond Book, de Mm~ 
di zMtberei recenfioribus Phenomenis, pag. 461. Jit era Di- 
vifioad Clarif/imi Mathematics VetriNon\i—--~im!tationemper 
f lures quadrantis anus introrfum defer iptos & diver fimode fub di- 
vifos procedit. ^ Etfiautem in hoc ipfa imprimis ingeniofa'Non'ri 
inventione, aliquid auctuarii loco exp edit ius a nobis additum eft, 
ita nt exterior arcus in plurimas portiuneulas dhidatur 5 neque is 
or do out numerus aremm fefe introrfum cone omit antium, quern ite 
prafinivit fed multo expeditior A> per feet ior obfervetur, tamen 
qniah<ec fubtilitas cum adpraxin deventum eft plush ab eat labor is 
qmrnfruttusfieq^ id in receffapr<eftet quod prima front e poUicetur, 
ut alibi plenius ojlendemus, idcirco apud nos dudum in ufu ej]e defiit. 
[ See more of this, pag. 6 2. Epiftolarum Jftronomicarum. ] 

From which way of Divifion, this of Hevelius ( which he 
afcribes to Hedreus, but is more properly afcribable to Pier- 
re Vernier^ as I fhall afterwards ftew ) is fomewhat different, 

D 2 and 



( at) 

and poffibly might.be the fame that Tick Brahe contrived to 
compendifie that of Nonius* 

The way then is this, defcribed by Bevelius y pag.i4.r;. 
Quadr antes contractures ita a me Junt adormti, ut Umbos eorum 
t ant urn in integros \& Jemigradus dijlinxerim\qu£ ut hac diftintfia 
non nemini admodum rudis videatur, Jufficit tamen ajfatim com- 
monfi aniis fingulis minutis primis\ dummodo perpendiculi excen* 
tro appenfi extremity limbum ftringens in ceruu particular [it Jub- 
divija, imo quod magisde quo non nemo fane mirabitur ? nonJolum- 
h<ec rudior limbi fubdivip Jufjiciens exhibendis fingulis minutis. 
primisjedetiampro denis qmnisquinetkm fingulis Jecundis in ma- 
joribm organis Ji videlicet nofirumlnftrumentum director ium adhi- 
beas, Oportet ut inferior iliius pars curiofffime & levifllmefti li- 
mata & levigata, ut limbum ntum aquabiltjfime quidem tangatfed 
mlLibt nimis adhere at > turn quovis loco liberrime pendsat atq\ di- 
vifionis tarn quadrantis quam perpendiculi- objervator rite di Jeer- 
nere vale at. Dividitur autem ifiud perpendiculum- hac r attorn r 
ft videlicet ftatwm 3 t [emigraduum in limbo perpendiculi accura* 
tijfime denotes ; idq'.pnmum in tres aquales partes, rurjumquam- 
libet trientem in decern dtvidas \ atq\ it a obtinebis fpatiola pauU 
admodum ampliora quamfyatiola unius femigradits, quia inter ca* 
pedo ^ipartium in 30 tranjmutata necejjario fiunt modice amplio- 
res. Attamenfi dwi [tones perpendiculi ad limbum quadrantis 
accedant circa extremitates perpendiculi, dijcrefantiola ilia divifio* 
num ab invicem vix ac ne vixcognojcitur :, circa medietatemvero. 
perpendiculi Jatis evident er. In medio limbo perpendiculi & di- 
viponumparvulus index & quidem inter 1 5 d* 1 6 (paciolum con- 
fiituiturpro dijcernendis integru & jewigradibus', quos accurate 
% Bus index tndkat, quando totumfjat mm perpendiculi in 3 o par- 
ibus divifum inipfo limbo quadrantis JJ at ium 3.1 pMtiumsxquifite 
[uhendit. ha tamen expreffa lege fi tot urn Uftrumentum absolute 
ab omni parte fit conftrutf.um; qumdo veroifte index puxiUm 
promotior exi§it integro aliquovel femigradu certiffimum eftindi- 
c'mm y obfirvationiminuta quidem .adharere autintegro aut Jem*-, 
graduiadnumeranda, fi index huk velMvkinior eft, Cogmjct- 
*tur autem minutorum numems ex eo, quando lineola aliqm diytft- 
wum inperpendkulocum una aliqua in limbo quadrantis pr or Jus in 
mam eandemq coincidit reffam* Nunquam enim nijl.unka ti- 
neokinp£rpendknlo cum altera in quadrante, fiexqmfitepcracU 



(29 ) 

[unt omnia cmnino concurrit. In ifto igitw utrmfjs UneoU 
"eoncurfu ubi una, eademq; videlicet Gonftituitur linen eft Urmmns 
ipforum minutorum velintegro gradni vei femigradui adh^ren- 
tium. 

This fame way is alfb made ufe of by Uevelim y for the Divi- 
fion of atl his larger Inftruments, as well as for the Divifion of 
thisfmaller, by fixing it upon the Perpendicular, asheaiter- ' 
wards mentions, cap.i$+ pag. 307. where healfo gives a fuller 
defcnption of it, to which 1 refer the Reader. 

The way indeed is exceeding ingenious, and very much im- 
proved by Uevelws, but yet ac the very belt it is very diffi- 
cu!t, both to make the Divifions, and much more d/fficult to 
diftinguifh them, as may be plainly enough feen even by that 
very Specimen pub li filed by Hevelim^ in the firft and fecond 
Figure of the Plare T. efpecially if it be viewed with a magni- 
fying Glafs or Lens 5 and I do wonder that Hevelim did not 
all this while think of making ufe ofa Lens, to make the D vi- 
fions and Diftin&ions appear more plain, without which Se- 
conds are not to be diftingaiflied, by thole kinds of Divifions 
even in an Inltrument of 10 foot Radius, and by the help of it 
they may be made and diftinguifhed, in Inftruments ofa quarter 
that bulk, as he may find, if he pleafe to make ufe of theflia!- 
loweft Objeft-Glafs of that Microfcope which he had from 
'London ; he may, I fay, by looking upon the Divifions of the 
firft and fecond Figures of che Table T. with his Microfcope, 
plainly detect how far thofe Divifions are fliort of accurate - 
nefs, and how many faults and inequalities the naked eye and 
unmaehined hand do commit. 

It is therefore one of my ways for dividing and diftingui fil- 
ing Divifions, to make ufe of one, two, or three Lenfes 3 where- 
by not only the eye is very much eafed, but. the judgment is ve- 
ry much augmented, and the hand directed, as I (hall after- 
wardsexpiain, when I come to fhew fome particular ways of 
making Divifions. 

But becaufe this Beneditifts lledrcus, from whom Uevelius 
affirms he received this invention of dividing the Limb of the 
Quadrant, was not fo ingenuous as to confefs that he received 
this invention from another, and becaufe perhaps the Book be- 
ing final 1, may have been longfince loft and forgotten, hiving 

accidentally 



( S o ) 

accidentally met with one, I fliall acquaint Hevelhs, that one 
Pierre Vernier (as he calls himfelf) Capita fo& Cbafiehm pour 
fa Majejle m Chafieau Dornans^ Gonjeiller, & General de fis 
Monnoiescm Cont'e de Bourgongne^ printed at Bruffels^ by Fran. 
m Vivien, 1 63 r. (to wic 1 2 years before Hedreus) aTreatife 
in French, which he calls, La confiruttion PUfage & les Propria 
etes du quadrant nouveau Mathematique, commt aufji la confirm 
ction de la table desjinus de minute en minutes fuccefiivement par 
un feul max i me. De plus un abrege defdiffs tables en une petite 
demipage avecfin ufage : &finallement la methode de trouver les 
angles d'un triangle par lac ognoijfance des coflez, & les cofies par 
les angles fans Vayde d' aucune table. In which he hath at larger 
and very plainly defcribed this way of dividing the Quadrant, 
to what accuratenefs is defired, and pretends it to be, as pof- 
fibly it was, an invention of his own. 

But to return where I left to Bevelius his Divifion on the 
Quadrant by the help of the Brafs-arm, I fay, againft this way, 
befides what I have already mentioned, I have a (econd Ob/e- 
dion, and that is,that it requires a mofi: exceeding great curio- 
fity and care to make that Metal Pendulum or Plumb of Brafs, 
fo as to be exa&ly of equal weight and make on both fides of the 
fuppofed middle Line, for if it be not fo, it may eafily vary 
not only fome Seconds, but even fome Minutes from its exact 
Perpendicularity, and if fo, 'tis to little purpofe all the for- 
mer curiofity about Subdivifions. 

Thirdly, The Perpendicular ought alwayes to be kept very 
clean from Duft, for if a little more Duft fettle on the one fide 
then on the other, the Perpendicularity will be vitiated, and 
all the curiofity elfe about the Obfervation will be loft. 

Fourthly, If the Pin on which this Brafs Perpendicular 
Jiangs be not of fome bignefs, it may eafily warp, or bend; and 
if it be of aconfiderablebignefs, it will not move eafily, and 
confeqtiently the Plumb will not hang tender, but ftiff; in both 
which cafes it can be of no ufe in the World for Aftronomical 
Observations. Further, if it hang loofe upon the Center, 
which it ma ft do to hang tender, then there will lye as material 
an Objection againft it, for its not moving true upon the Cen- 
ter of the Inftrument; and therefore upon the whole matter I 
conclude it to be an Invention indeed of great fub^mity and 

fubtlenefs 



(31 ) 

fubtlenefs,but of little or no ufe for Aftronomy,to which Heve- 
litu applies ir. He had much better therefore have been content 
to have followed Ticbo Erahe^ud made ufeofa common Plumb 
Line and Diagonal Divifions, where there is occafion for them, 
for that is true and practicably capable of exhibiting the Subdi- 
vifions of a Degree,as Minute,asare neceffary to commonSights. 

Jn the next place, before he leaves the Defcriptions of 
thefe three fmaller Quadrants , he mentions an Invention 
of his whereby he fixes the Quadrant in any altitude , and 
eafily moves it fteadily into any pofture denied by the help 
of Screws. This Invention of his own contrivance he doth 
indeed very highly applaud, infomuch that he believes no good 
Aftronomical Observations can be made without it. But he 
muft pardon me if I am not altogether of his mind ; I grant in- 
deed the thing is exceedingly convenient, in comparison with 
any yet ufed, if it be well made, and that the way of apply ing it 
to the Quadrant be very facil and eafie. But 'tis not alway fo 
neceffary, but that Obfervations may be as conveniently made 
without it, as I fhall afterward (hew, in the Defcription of the 
moveable Axis, for continuing the Inftrument in the Plain of 
the Object , whether a Diftance or an Altitude be to be 
taken. 

In the next place he proceeds to defcribe his large Qua- 
drant of Brafs adjufted feas to take Altitudes and Azimuths , 
of which he makes a full and particular defcription $ but the 
moft confiderable thing that is new in it is , that inftead of a 
Screw ufed by Itch* for lifting and moving the Arm with 
Sights, he makes ufe of two Lines poys'd with Plumbets, by 
the pulling of this or that of which he is able toraife or fink 
the Ruler with Sights, all the reft of the contrivance being 
to make it ftand perpendicularly in any Azimuth, which i think 
may be done to greater certainty with lefs trouble, by a way 
I fhall afterwards fliew : As an Effential part of this Inftru- 
ment, he takes occafion to give the defcription of the Turret 
or Obfervatory which he built for it, and the feveral contri- 
vances about it, which I now omit. 

The ufe he made of this Inftrument was for the taking the 
Meridian Altitudes of the Sun, of which he affirms to have 
taken a very great number, efpeciallyfuchas were of princi- 
pal 



( 3* ) 

pal tiTefor the regulating the motion of the Sun: Such as the 
Solftitial and ^Equinoftial Altitudes, of which I hope we may 
expetf an account in the fecond and third Part of his Machina, 
Cdeflh. I know not to what exaftnefs he hath proceeded in 
taking his Meridian Altitudes of the Sun ; but had he proceeded 
in the way by Telefcopes , he might have taken all his Alti- 
tudes of that kind to a (ingle Second, with great eafe and cer- 
tainty. 

And upon this occafion I hope it will not be unacceptable 
to my Agronomical Reader to hint a very expeditious and ex- 
ceeding accurate way of making a Catalogue of all the vifible , 
as well as the mojflconfiderableTelefcopical Stars of the Hea- 
ven* For the doing of which there will not need a. tenth pare 
fo much time as for the other wayes that have already been 
made ufe of, and yet will very much exceed them all in accu- 
ratenefsand certainty. The way then in flion is nothing but 
this : Let there be made a very large mural Quadrant, or rather 
Semicircle, of 30 foot Radius, fixed exattly in the Meridian 
againft a Wall made of fquared Stones, well joy need and cramp- 
ed together, andfetledon a foundation very firmand iblid, to 
prevent all manner of flaking and fwarving. Let the rim of 
this be made of Brafs Plates, flayed in their due pofture by 
cramps or bars of Iron fixed in the Wall, by running them with 
Lead : then having divided this Semicircle into 1 So Degrees , 
and fubdivided each Degree by the hblp of Diagonals, on a flat 
and well poliflit Plate of Glafs, according to the way I before 
defcribed into Minutes and Seconds : adapt to it a 30 foot Te- 
lefcope, fo that the Tube fliail not warp, nor the GlafTes devi- 
ate out of their true pofture ; the Focus of the Object Giafs 
make to be exaftly upon theedge of the Brafs Limb, fo that by 
the help of the Eye-glafs, which is a deep Convex, the punclu- 
alplaee or altitude of a Sear to a quarter of a hairs breadth, e- 
ven to Seconds of a Minute, may be difcover'd ; the trouble 
of dividing this Quadrant will be no more then of one of an 
ordinary fize, the fubdivifion of one Degree fubdividing and 
examining all the reft. The way of making the Tube of the 
Telefcope fo as not confiderably to bend, may bedonefome- 
whatafcerthat way of ftifFning the Tubes of very long Tele- 
fcope% which I communicated toHeve/m, and you will find 

at 



(33) 

at large defcribed in this Treatifeof Hevelius : Save only, that 
inftead of Ropes which I firft made ufe of, / rather commend 
Tommy Braces of Wood. Now though notwithstanding all 
the Diligence that can be this way ufed, the Tube do fomewhat 
bend in the middle, yet it can be of no manner of fignificancy 
as to the vitiating theObfer vationjfince firfr,theObjed Glafs al- 
ways ftandeth in the fame poilure as to theCenter,and fecondly, 
the Focas thereof isexaftiy in the edge of the Limb. 

Furtheryo prevent the inconvenience of looking up or in any 
other uneafie pofture by the help of a reflex Metil one may al- 
ways lookHorizontally,that is, perpendicularly to the plain of* 
the Wall or Mural QgadrancAnd to prevent the trouble and la- 
bour of moving or lifting the Tube by the help of a long yard 
poyfed upon Centers on a Frame before the faid Inftrumenr, 
both the Tube & Arm for theSight,and the Seat on which theOb- 
fervator (its, may becounterpoifed, fo that by turning a Win- 
die, he may eafily raife hirafelf with the Tube to anypofture 
defired. The Object Glafs is juft before the Center, and the 
Eye Glafs looketh direftly on the Divifions of the Limb , and 
there is nothing to drain or ftir the Jnftrument it felf , nor can 
the warping of the Tube, if there fliould be any, have any ef- 
fect on the Obfervation : Of this I may fay more on another 
occafion. By this means (in one Nights Obfervation) the De- 
clinations of fome handreds of Stars may be taken to a Second 
by one (ingle Obfervator, having only one or two Affifhnts to 
write down the Obfervations as faft as made. And at the fame 
time the right Afcenfion of every one of them may be taken by 
the help of a very accurate Compound-circular Pendulum 
Clock, which I fliall elfewhere defcribe, denoting even to 
of a Second of time the appulfe of the Star to the Meridian : 
There needs indeed great exaftnefs in every part of this Appa- 
ratus, and 'twill not be done without a confiderable charge,and 
much labour and diligence in the performance thereof; but if 
we compare it with the methods and wayes that have been hi- 
therto ufed, wefhall certainly find that the Obfervations will 
be near 30 times more accurate, the charge not a quarter, and 
the labour not near a tenth pare fo much as in other wtyes made 
ufe of by Ticho and Hevelw. And though ic may be objected 
againfl: this way (which indeed may be much more fo againfi: 

E any 



(?4> 

apy other) that the refrafiion of the Air will considerably vary 
the Declination of fuch Stars as are very far South, yet fince 
the fame Inftrument affords a way beyond any in the World 
for the difcovering thefeveral Refractions of the Air at feveral 
Altitudes above the Horizon, to the accuratenefs of a Second, 
by taking the Altitude of fuch Stars as never fet in the North, 
in the greateft and leaft Altitude above the Horizon 5 a Table 
of fuch Refractions will eafily re&ifie the Declination of the 
other Stars to as great accuratenefs* This Subject doth deferve 
a much larger and more particular Defcription of every Branch 
ftereof, and the Incouragement of fome Prince, whofe Name 
and Honour will thereby be.Regiltred among thofe glorious Ce* 
leftial' Bodies to all Pofterity , and the fueceeding Learned 
World will be obliged to celebrate his memory. But I fear 
this Age will hardly y eild another Jlphonjw, another Ticho. or 
another Uevelim, who have not fpared to expend their utmoft 
Indeavours in performing this task, though by other methods* 
But leaving this for another time, I fhall proceed. 

In the third place then he goes on to defcribe his great Ho- 
rizontal voluble Brafs Quadrant, of which he fays,' he does 
not believe that ever the like was made by any, if the.fplendici 
jtffuratM and the whole Fabrick thereof be confiderU It is 
in Diameter fix foot and an half, and ferves, as he affirms, to 
take Altitudes to Seconds; butyet he is necefTitated to allow, 
that it is fliort. both of Ticho's largewooden Quadrant, and of 
his large mural Quadrant $ nor do I fee any reafon why tkbos 
mural Quadrant fibould not take Meridian Altitudes fomewhat 
more accurately, fince I believe his Sights every whit as good, 
and his Divifions altogether as exad ; what he might fail in di- 
ligence, I cannot fay. I do believe this Inftrumenr to be an 
exceeding good one of the kind, and that he hath from much 
practice and experience found out many contrivances, in order 
10 the making it convenient 'to makeObfervations, and he hath 
not fpared for cot, pains, ftudy and induflry, for the corn- 
pleating thereof; but ftill whether he be arrived to the gi eat eft 
perfection, or to fo great as to take Altitudes to Seconds, fecins 
to me very dubious, and ifhe made ufe of the Sights before-de- 
fcribed," wholly impoflible. For firft, a -Degree upcn the 
Limb is but about f of an inch, and confequently a Minute is 

hue 



(3S ) 

but the 50th. part of an inch, and a Second but the 3000th. 
part of an inch, which he that can diftinguiffi with his naked 
eye, hath better then 1,-orT fear, any man now living* Shorc- 
fiohted men/ 1 grant, can do much toward the diftinguifhing 
very minute Divifions, by being able to bring the Objed very 
near the eye, but the moft fhort-fighted muft be yet very much 
fhortriedby GlafTes, before he will be able to diftinguifli the 
3000th. part of an inch, and when he hath diitinguifhedit, 
which he may poflibly do with a Microfcope, how will he di- 
ftinguifh of the Penumbra, which is not certain even to a Mi- 
nute? And though it may be faid, it is the lame, round the 
Circle, and the Circle is the true bignefs of the Sun, fo that if 
a Circle of a bignefs, anfwering to the Diameter of the Sun, 
and the Diftance of the lower Sight from the upper be defcri- 
bed on the lower Sight, it muft bound the Limb of the Sun, 
and that confequeatly it will be eafie to diftinguifli when that 
Circle is perfectly fil I'd with the figure of the Sun, admitted 
through" the hole in the upper Sight. lanfwer, That this feems 
very probable and eafie, and is indeed believ'dandafferted fo 
by Optical Writers : iBut yet 'tis quite other wife 5 for not to 
mention that there is confeifedby all, that the Penumbra of this 
Circle muft be.asbig at leaft as the Diameter of the hole above, 
through which it is traje&ed, which cannot be lefs then a Mi- 
nute ; I fay, that expense doth demonftrate that it is quite 
otherways, and that the Limb of this Image painted on the low- 
er Sight is terminated with a Penumbra, which is fometimes 
ftve or fix times bigger then the Diameter of the hole, and which 
is yet ftranger, thefmallerthe hole be, the bigger is the Ten- 
umbra, and the bigger (to a certain Degree) the lefs, but there 
is no bignefs which will take it of quite, and the Diameter of 
the Sun that way taken, is fometimes bigger and fometimes lefs 
.then it ought, and that to a very confiderable quantity : Of 
which, and feveral other very ftrange proprieties of Light, I 
fhall hereafter fay more on another.Subjed., 

But to proceed. That he hath made* '.this Inftrument his 
chiefeft,you may perceive by his patheticai defcribing thereof; 
for he fays of it, fag, 1 84. Ad commodiorem hujus quadrmtis 
nfemjot ac tot &&mimcul& recens excogitata atq\ hmc orgAno appli- 
cAtdfuere,ut nefciam Iquibmfnmum inchoare deieam* hno 

E 2 . ctitmR 



( 36) 

ttiamfivel maxime veUm^nullo tamen modo omnia &fingula adeo 
perfpicuevel de linear evel defcribere potero,ut univerjipr£primis 
quifimilia baud ipjimet oculis ufurparunt qu<evis re Be ac plane in- 
tel/igant, quinetiam credos velim utut aliis funt attentiores atq; 
hujus ret bene gnaros, aliquoties fane hocce Infirumentum vifuros 
antequam dimidiam tantam partem debit e animadvert ant ac pie- 
niffime comprehendant. §£juippe & verumfateor necipfe egojicet 
Jingula ex meo folo cerebro prodierint ac confetta fuerint t poffem 
adeo dijlintfe tibi eumfub afpebtum fonere giji mi hi hocce orga* 
mum fub oculU affidue verfaretur. Nihilotamen minm dabo ope- 
yam> ut quantum fieri poter it \dilucide omnia prof onam/eliqua vert; 
exercitatis cteli metaloribm ulterim rimanAa & perquirenda 
commit am, &.c. 

Andfo he proceeds with the Defcription of this Quadrant, 
and the apparatus about it, and firft, he tells us of the weight 
of this Inftrument, that it was 80/. Next, ofthefliapeof the 
Turret in which it was fixt, which is indeed very convenient 
and ingenious, it being fo contrived, as to be voluble or con- 
vertible upon Truckles, having one only fide open, and in- 
clos'd on all fides clfe, fo that neither the Obfervator nor the 
Quadrant was much expos'd to the injury of the weather, 
which is indeedof no final 1 ufe in Agronomical Obfervations.. 
But this may be done many other ways alfo. He tells us fur- 
ther of the admirable and prodigious ufe of Screws, in order 
to the fetting and fixing the Quadrant. Next, As to the giy- 
ing a motion to it, in order to follow the Sun and fixed Stars 
In their diurnal motion. Thirdly, As to perform all the Sub- 
divillons of a Degree, not only into Minutes but into fmgle Se- 
conds. To all which f fay firft, As to the ufe of the (ball' 
Band-fcrews, I do grant, that in fome cafes they may have 
their couveniency, as to the moving and ftaying the Inftru- 
ment. But then fince he is fain to make ufe of two Screws, 
whereby both the hands muft be imploy'd to manage thefe 
Screws, I judge them too troublefom for that ufe, and that 
there is a much better way, whereby the Quadrant being once 
fet into the Azimuth of the Stars, it ftall continue to be fo, 
and to move along with it, without any trouble to the Obfer- 
vator, fo long as the Obfervator hath occafion to have it re- 
main fi> 5 vhich (that I may hint that o»ly now by the By) is a 

Audi. 



C 37 ) 
final 1 Automaton, which [hall continue it for many hours ex- 
a#ly, in the Azimuth of the Star deiired, of which more here- 
after. 

Next, Whereas he affirms this way capable to ihew Seconds 
as well as Minutes, I granc it may be capable ; but then 1 muft 
further affirm* that he hath not at all (hewed how that can be 
done, nor is it indeed feafible in his- way, for he fhews us not 
any way how to fet it, that is, fix it certainly to any Degree: 
Now if he be not fure in the fixing It exactly to a Second, up- 
on that Degree where he would begin his Divifion, *tis a vain 
thing to be fo accurate in the other Dimenfion, for he cannot 
be more certain, ( let him be never lb curious in the Subdivifi- 
on with his Screw) then he is certain in the firft fixing of his 
Screw to the Degree, for whatever he varies from the Degree 
in the fetting, he varies at leaft as much in the Subdivifions, and 
confequently unlefs that be fome ways taken care of, which I 
do not find, 'tis a nicety withoutufe. 

To conclude therefore,.! fay, the Frameof this Jnftrument 
rs extraordinary good, and by the help of fome additions, as 
to the Sights, Divifions, Perpendicular and ErecTion, might 
be made as good as need be defired for any ^Q in Aftronomy, 
and 40 times better then what it is now made and defcribed by 
Hevelius, or then any I have yet heard of to be made in the 
World. But as it is, it is not more exad then the large Infrra- 
ments of the Noble Tkhd Brahe, which he ufed 100 years 
fince, and much fhort of his mural Quadrant, for taking Meri- 
dional Heights. 

He proceeds to the Defcription of his new and large Brafs 
Sextant offix foot Radius : The Sightsand the Divifions there- 
of are in nothing differing from thofe of the Quadrant, nor do 
I find any thing very confiderable in the Defcription thereof; 
it was made ufe of by two perfons in the fame manner as the . 
former Sextan^ and like that of Tuho $ but what grand incon- 
veniences do attend that way of Obfervation, I (hall after- 
wards (hew, when I come to explain how one perfon alone 
may be able to do it withlefs trouble by half, and ten times 
moreexadtnefs. 

But by the way, I cannot but take notice of what Heveltta 
ingenioufly confefles, of the great difficulty there is in taking 

the 



( 3* ) 

tie Diflance of fixt Stars from the Moon, which is from no- 
thing elfc but the imperfections of his Common Sights, and all 
that difficulty vanifhes, if the Sights be made anotherway. 
Next, He feems to make it a much more difficult bufinefs, to 
take the Diftance of the Sun from Venm\ when flie isfeen in the 
day-r.me 5 but by a way I fhall hereafter (Lew, it will not only 
be eaOe to take the Diftance of the Sun in the day-time from Ve* 
nm, but from $fflm\ from Jupiter y nay, from feveral of the 
fixt Stars, 

i Oiail pafs by therefore his Apparatus > which feems very 
great and chargeable, fince I fhall elfe-where fhew a (ingle, 
plain way, without any trouble or perplexity, how the mat- 
ter may be quite other wife ordered, much to, the advantage of 
the Obfervator. 

As to what he afTerts of his extraordinary care, diligence 
and pains, in dividing and examining the truth of his Instru- 
ment, I do no ways doubt ir, but that he hath proceeded as 
far as it was poflible for one to do in that way he made ufe of, 
but might have faved much of it, if he had thought of the way 
by Diagonals on Glafs, which I have already defcribed. Yet 
I fliould have been very glad to have feen the Diftances, which 
he mentions to have taken of eight fixt Stars near the Eclip- 
tick, to wit, Lucid* ArietU & Palilicii, Talilhii & FoUucis, 
fcllucis & Reguli, Reguli & Spic<e, rSpic<g & in manu Serpent a- 
rii, in manu Serfentarii & AquiU, A^uiU & Marchab, Mar- 
chab & Lucids Arietu, and that to fo great exaGnefs, as not to 
mifs one (ingle Second in the whole Circle of the Heavens, ta- 
ken at eight Obfervations. For to me indeed, it feems one of 
the greatefi affirmations I ever met withal, and not lefs then hu- 
manely impD-ffible,were there no Refra&ion in the Air, and did 
all the Objects (land (till in the Horizon, but the Refraction 
of the Air, were it much lefs then it is granted by all, would 
neceflfarily caufe a variety of a great number of Seconds. And 
I durft undertake to demonftrate it to any, as plainly as any 
Geometrical Propofition, that it was wholly impoffible for 
him, with all or any of the Instruments he hath defcribed, to 
make any one of thefe Obfervations, to the certainty of 30 Se- 
conds, whence if that uncertainty be 8 times multiplied, it 
will follow, he cannot be certain in the whole Circle to 240 

Seconds, 



(39) 

Seconds, or 4 Minutes, which how much it is -differing from 
one (ingte Second, any one may; idg. 

I had many other things to have added, which have Qccurr'd 
tome in the perufingof Hevelms his Book, but I will fay no 
more atprefentby.way of Objection, having, I fear, wearied 
the Reader, with fliewinghim my doubts and fcruples, efpe- 
eially about the imperfection of that way of Sights and Divi- 
sions made ufe of by him : Only, to make my Reader fome 
mends for his patience, I ilia: I defcribe a fliort Apparatus ^hich 
J have contrived for this purpofe, and in the doing there- 
of, flh'ail be as plain and brief as pofilble the matter will bear. 

Since the reading thefe Ledures, the Author having been 
acquainted, that fome considerable Objections had been made 
again ft tbe certainty and accuratenefs of his InCiruments, and 
that I had affirmed it impoffible to perform what he had pro- 
mi fed in his Book, he returns his Sentiments thereof in aLeuer 
to Mr* Oldenburg, to this effeft : 

««— « Cater urn percipio vejlrates non omnes miki adfiipulari 
in ijlo Dioptramm negotio, de quibm in machine me a ccelejlis 
Organographia traffavi , verum etiamji Cla. Hookius & tla. 
Flamftedius aliiq\ plane aliter [entiant^experientia tamen quotidi* 
ana me edocuit atq^ etiamnum docetyem longe aliter fe habere in 
magnis illis organic,- quadrantibm [cilice t [extmtibus & oU anti- 
bus imprimis quadrantibus dz>imuthalibus aliuq , quadrant ibus ' re- 
gulis confiruffis, qua, nempe adeo procliviter commoveri & tnver- 
ti (dum Dkptr<elelefc-Qpic£ examinantur} imo ntiilo mo do pfjjunt, 
ut quidem Inftrumenta ilia*, trium quatuorve pedum perfendtailo 
conjirucla. Reicumfrimis in eo conftftit^ quod nullam plane ob- 
[ervationem fufcipere pofftnt juis Dioptris Telefcopicis mftprhs dc- 
nuo e<tA examinent acreffifieent $ in quo tame n examine vdria 
via, tumjugiterntutftudiojifiime iliud fufcipiatur hallucimri da* 
tur. Adh&c in quadrmttbus Azimutbahbus, off ant thus &fex- 
tantibus, qua ratione examen iftud adeo accurate mmquam non 
haudmagno negptio tempori[q\ difpendio injlitui pofiit, project mn- 
dum capio, vix mihiperfuadeo ullibi adhuc ullum aliquem magnum 
quoddam Injlrumentum 6 vel y pedum utpotefext. off ant, vel ' qua- 
drant em cum regulavelquadrant.A&im.cump'mnacidiis Dioptricls, 
conftruijfe, eumqs ad ccelum felici aliquo fucceffu adhihmlfe, & 
quicquam [olide obfervaffe j Ji tentajfct ac per anncs aliquot objer- 

vatiom? 



C 4° ) 

vAtiwihus continue invigilaffet fine dubk aiiter fentiret. Hoc 
negotiant enim nonfolum in eoconfiftit quod ft eU^ aliquant o diftin- 
elms confp kiantu r (qumquamfixA ab eo qui vifu pollet & exerci- 
tat as eft a que bene nudis oculis difcernantur) fed an Instrument a ab 
omni parte cor r eft e commonftrent, an pinnacidia Telefcopka Inftru- 
mentis toties ad quafvis obfervationes rite imponi & tuto confer- 
van que ant \ de quibus quidem id onfni tempore a que pracife fieri 
poffe valde dubito, ^juare Clariffimosillos viros bumaniftime roga- 
tos volo ni(i jam poftideant ejufmodi vaftiftima organa utpotefext. 
oft ant. & quadrant. jiz*im. Dioptris telefcopicis munita, eaq\ cat- 
locontinmadmoneant, fufpendant judicium panlulum, donee longa 
annorumferie expertifuerint baud fuiffe multoties egregie elufos. 
Nam ex una alt crave obfervatione quadrant, aliquo levioriperpen* 
diculo gaudenti obtenta, res h#c noneft decidenda, fed ft quisper 
100" amplius annos affidue obfervaverint, tumab ovoferiamftel* 
larum reftitutionem per didantias fufciperit, poterit qu<edam cer- 
tiora in medium hac de re prof err e. De reliquo fatis mirari ne- 
queo, eas omnes qui ejufmodi Dioptris teiefcopkis gaudent, non- 
dum locorumfuorufn^ elevationempoli ubi degunt & obfervatimes 
peragunt, quantum fciam reUe & omnino pracife determinate &> 
ftabiliviffe. Hucufq\ enim ad aliquot minuta integra Parifiis ele- 
vatiopoli nondum eft definita, alii quippe eandem obfervationem 
48. 49' alii $0'. alii$i\ alii $2', alii 53', alii 54', $$' imoam- 
pliorem adhuc ftatuerunt : f cut i lege re eft ex difcertatione Petri 
Petiti de latitudine Lutctiae, fed nolo in bis prolixius effe\ad obfer- 
vatione s if fas provoco^ tempus aliquando docehit quorum obfervati- 
one s univerfas accuratiores fuer int.fi modo nonnulli cenfuram fuam 
eo u fq\rcjkere poffent. Nam video aliquos wter quos etiamCl. 
Fl \n\Redh sinvenitur^ prout ex Epiftola ad Cafllnum apparet, 
ja m judicium de no (Iris qualibus obfervationibus tuliffe, priufquam 
ill** 6 adhuc viderunt examinarunt vel quicquam de its cognoverunt. 
No^o quidem vanus effe rerum mearumjaftator, nee unquammihi 
im a ginatus fum rem in omni ifto negotio circa fcilket reftitutionem 
^Jlarum fixarttm acu omnino tetigiffe vel t anger e poffe. Sed 
bocce pen'nus mibi imaginorfitotum iftud negotium Dioptris Telef- 
copicis fufcepiffem, quod non folum plurimos annos examinibus tri- 
vi(fem, fedfyeftne dubio v aria via ( de qua hie non eft difcerendi 
licus) cecidiffem. Exinde gratdor mihi me ad earn fententi am non- 
dum tranfit(fe, ac me mea methodo univerfa perfeciffe fe quicquid 

prsftitum 



C 4* ) 

profit urn Dei benejicio erit: an nihil amplik ( tit putat CUnf, 
Fiamftedius) quam hactenw & quoufq; progreffum faeritjiberum 
erit cuiq\cum deinde viderit judicium fuumexpnere quinetiam 
integrum eritalium novum integrum catalogumfuperadditis tot ac 
tot centenis nowjixis, hactenu* negletfis alia ratione confiruere: 
Verum nondum video an cur a h<ec moleftiffima, udiofiffima ac la- 
borioJilJima i qu£ non nijimultorum anmrum vigiliis fufcipi ejrper- 
agipotejl.aliquem adhucferio tangat. Unam aut alter am fieliam ope 
Telefcopii vel Dioftrarum Telefcopharum, dum pracipuas ac majo- 
resfixasearumq- y int ere ape dines fupponimm ccrretfas ad debit um 
locum deducere, turn nonnunquam dijlantias nonnullas ftelkrum ca* 
*pere h&c ludicra funt * fed omnes conjunclim fecundum longum & 
latum rejlituere, turn duttu continuo (mgulis ferenis diebm acno- 
ttibM) tarn altitudinnm [olarium quam reliquarum ftellarum ob- 
fervationibus operam dare,easq\ orbi exfonere ut pateat motuum 
harmonia atq\ hjlrumentorum certitudo, hoc artis hoc labmseft. 
Quando obfervationes 20 vel 30 annorum [patio continuatas ab 
utraq\ parte aliquando habebimm y nimirum tarn qua Dioptris te- 
le fcopicis quam qua folummodo noftm ex ccelo deprompta funt res 
omnino clarior erit. Int ere a quilibet fruatur fuo ingenio, acfua 
ratione yro libit u rem tentet. Honorifaum nobis omnibus erit pro 
modulo nojlro a Deo concejfo, ret literariaincrementumvaria via 
promovere. 

To this Letter of Hevelius I have this to anfwer, That the 
Author neither hath, had, nor can have any experience, to 
fliew Telefcopical Sights not to be as good as the Common, or 
that they are Iefs applicable to large Quadrants, Sextants, 
Oflants, or Azimuth Quadrants, or to any other Quadrants 
furniffced with Rules, and fo fixf, that they cannot be cafily 
inverted, or turned, then they are to Quadrants or Inftm- 
ments of 3 or 4 foot Radius. Nor is hi Reafonagainft them 
of any validity, that noObfefvation can be made, without a 
repeated previous examination and rectification of the Sights, 
in which, fays he, notwithftandingall the care and diligence, 
there is a Reafon of failure and miftake* For fir/}, J fay, 
There is lefs need of rectifying the Inflruments or Sights, af- 
ter they have been once adjufted, then of Inflruments with 
Common Sights, all things being perfectly fixt, and fo ftrong 

F as 



( 42 ) 

as not eafily to be itirred or removed. I now begin to fear, 
that he hath not a true notion of the manner of performing the 
fame, otherwife he would never have propounded fuch an 
Objection ; and indeed he feems to fay as much in the following 
words , &M rltione ex time n iliid omni tempore commode & 
(we magno temforis dijjendio injiituifofjit pvofeffo nondum CApio. 
Though I am very forry that he fhould be fo:for firft,I thought 
I had about 9 years fmce, explain'd to him the w ay, when I ex- 
horted him by all means to the ufe thereof; at leaft if he had 
not under (food it thereby, I fhould, upon his defire, have 
fent him a more ample and particular Defer iption thereof, or 
have procured an Inftrument of that kind made and fitted for 
him here. But I fear, he had beenfome ways or other pre- 
poffeft or prejudiced againft them, before I writ fir ft unto 
him concerning them, at leaft before he writ that Anfwer, 
which I have before printed in the 5 and 6 Pages, for thereby 
it appears, that he was then of the fame opinion he feems now 
to continue of. And whereas he thinks, that no tryal hath 
ever been made of Telefcopical Sights, to a large Inftrument 
of 6 or 9 foot, I do allure him, (and I mif- remember, ifldio^ 
not then acquaint him with as much > that I had then by me fe- 
vera!, and particularly one of Sr. Chrippher Wren's inventi- 
on, furniilied with two Perfpeftive Sights of 6 foot long each, 
which I made ufe of for examining the motions of the Comet," 
in the year 1665. And if the fame thing can be better done 
with a Quadrant of 6 inches Radius^ then he can perform with 
one of 6 foot the common way, I think he might have con- 
cluded at leaft, that the fame thing would be 10 times better 
done in one of 6 foot Radius, made after the fame manner ; of 
this, I am fure, I gave him then an account. Now it is not 
with thefe kinds of Inftruments, as it is with Common Inftru- 
ments, where 'tis not poiTible to make any better then one may 
be made of 3 foot Radms, becaufe that is capable of Divifions, 
accurate enough ro reach the power of the naked eye ; but In- 
ftruments with Telefcopical Sights, are capable to be made to 
diftinguifti minutes, feconds, nay fingle thirds, if they be pro- ' 
portionably augmented. Nor is there any need that a man 
mil ft ma ke 7 years tryal of an Inftrumenr, before he can be cer- 
tain of the greater excellency thereof, for I can be as certain 

with 



C 43 ) 

with 3 or 4 times viewing an Objcd through a Teiefcope, and 
with my naked eye, that I can fee it better, and difHnguift 
many more and much fmaller parts in it through the Tel ef- 
cope, then I can with my naked eye, as f could be, fuppofing 
I had been viewing it 20 years together. But yet I muft af- 
fure Eevelm, my experience hath not depended upon 3 or 
4 tryals only ; I cannot choofe but wonder why he fliould be 
of that opinion, who hath not been iefs exercifed in the ufe of 
the Teiefcope, then any at prefent in Europe : Poflibly indeed 
his Telefcopes were not altogether fo good as now they are 
made, yetfurelam, he favv more with them then anyone can 
fee without them, as will fufficiently appear by his Phafesof 
the Moon, Jupiter and Saturn.. But I hope he * will not won- 
der at me, though I do now venture to affirm, without (laying 
10 years or more to make Obfervations, that I can do more 
with a Quadrant, Sextant or Oflant, of 1 foot Radius, fur- 
nifhed with Telefcopical Sights and Screws, then can poffibly 
be done with any other Inftrument, furnifliedonly with Corn- 
mon Sights, though io, 2©, 30, nay threefcore foot Radius; 
nor does ic at all follow, that the Latitude of Paris is not yet 
exa&ly known, becaufe MonfieurF^/V was ignorant of it ; 
but it rather fliews, that Obfervations made with Common 
Sights, ( fuch as I fuppofe Monfieur Petit's Inftruments and 
others, before the publifiiing of his Book were ) are no ways 
capable of certainty to a minute or two. 

But I have done, and am forry I have been forced to fay fo 
much in vindication of Telefcopical Sights ; and that in the 
doing thereof, I have been neceflnated to take notice of the 
imperfections, that are the infeparable concomitants of In- 
ftruments made with Common Sights. Nor fLould I have pub- 
lished thefe my thoughts, had I not found them fo highy de- 
cryed by a perfon of fo great Authority, fearing that thereby 
other Obfervators might have been deterrM from making any 
ufe of them, and fo the further progrefs of Aftronomy nvoht 
have been hindred. Nor would I willingly be thought to de- 
predate or undervalue the Works and performances of a perfon, 
fo highly meriting the thanks of all the learned World, both 
far his great and liberal expence, and for his vair pains, ca^e 
and diligence in the performing a Work fo highly 11 fefu 11 to 

F 2 Aftronomy 



( 44 ) 

Aftronomy and Navigation, and offuch infinite tedium, trou- 
ble, labour and coft, to the undertaker. 1 do not in the 
lead doubt, but that it will be a Work worthy Co excellent a 
perfon, of perpetual efteem and fame, and much preferrable 
to any thing yet done of the like kind in the World, and that 
he hath gone as far as it was poffible for humane induftry to go 
with Inftruuments of that kind, and that his Inftruments were 
as exaft, and compleat, and fit for ufe, as fuch Inftruments 
with CommonSights could be made, and that he hath calcula- 
ted them with all the skil and care imaginable, and deliver'd 
them with all the candor and integrity. But yet I would not 
have the World to look upon thefe as the bound o^mn ultra 
of humane induftry, nor be perfwaded from the ufe and im- 
provement of Telefcopical Sights, nor from contriving other 
ways of dividing, fixing, managing and ufing Inftruments for 
celeftialObfervations, then what are here prefer i bed by He- 
velius. For I can allure them, that I have my felf thought of, 
and inVmall modules try 'd fome fcores of ways, for perfeding 
Inftruments for taking of Angles, Diftances, Altitudes, Levels, 
and the like, very convenient and manageable, ail of which 
maybe ufed at Land, and fome at Sea, and could defcribe 2 
or 3 hundred forts, each of which fhould be every whit as ac- 
curate as thelargeft of Heveliw here defcribed, and fome of 
them 40, ^o, nay 60 times more accurate, and yet everyone 
differing one from another in fome or other circumftantial and 
eflential part. And that this may not feem altogether fo 
ftrange, I will aflure them, that I have contrived above 20 
ways for dividing the Instrument, each of them as much di- 
ftinft from each other as this of Eeveliut, and that of Diago- 
nals, and yet everyone capable of as great certainty and ex- 
actnefs at leaft, and fome of them 100 times more, lhave 
above a dozen feveral ways ofadjufting the Perpendicularity or 
Horizontality of Inftruments, all as exaft as the common Per- 
pendicular, and fome of them very much more, even to what 
accuratenefs fliall be defired, and yet each of thefe very dif-. 
fering one from another. I have as many differing kinds of 
Sights, for improving, directing, adjufting and afcertaining 
the Sight, fome of which are applicable to fome particular 
ufes, but fome for all, by means of which that part alfo may 

be 



(4* ) 

be improved to what accuratenefs is defired. I have various 
ways of fixing thofe Inftruments, and appropriating them for 
this, that, or the other particular ufe. I have various mecha- 
nical ways for making and working the feveral parts of them 
with great expedition and certainty, which is a knowledge 
not lefs ufeful then the knowledge of the theory and ufe of them 
when made, therebeing fo very few to be found in the World 
that can or will perform it. I have a mechanical way of cal- 
culating and performing Arithmetical operations, much quick- 
er and more certainly then can be done by the help of Loga- 
rithms, which compleats the whole buiinefs of mea Airing An- 
gles. Thefe I mention, that I may excite the World to en- 
quire a little farther into the improvement of Sciences, and 
not think that either they or their predecefTors have attained 
the utmoft perfections of anyone part of knowledge, and to 
throw off that lazy and pernitious principle, of being con- 
tented to know as much as their Fathers, Grandfathers, or 
great Grandfathers ever did', and to think they know enough, 
becaufe they know fomewhat more then the generality of the 
World befides: Reptat humi picmq;vult, delo refiat itur, 
Calo tentabimu* ire. Let us fee what the improvement of In- 
ftruments can produce. 

And now to make my Reader fome amends for his patience, 
I fhali give a Specimen r*. two, of each of the feveral parts 
that belong to the perfecting of celeftial Instruments: And 
this I (hall do, in the Defer ipt ion of an Instrument for taking 
all manner of Angles and Diftances in the Heavens, which if in- 
creafed in bulk, is capable of as great accuratenefs, as the 
Air or Atmofphere wtfl ever permit celeftial Obfervations to 
be made. Its perfection confifts in feven feveral particulars. 
i. In the Sights, which are fuch as may be made to difcover 
the minuter! part difcoverable in an Object, they do no ways 
ftraintheeye, and are fit for all Sights, whether (hort-fighted 
or o\d y &c. 2» la the Divifions,which are fuch as will diflin- 
guifh the Angle, as minutely as the Sights will diftinguifli the 
parts or Objects. 3, In the Sights, being fo contrived, that 
with one glance of. the eye, both the Obje&s though a Semi- 
circle diftant, are at once diltinguifhed and feen together. 
4. In the method of fating 't exaftly perpendicular to a Se- 

CPiltJ, 



( 40 
cond, if need be.. ' $. In its fixation and motion, it being fo 
fixed and moved, that if once fet to the Objefts, it continues 
to move along with them, fo long as 'tis neceffary to continue, 
or be very, certain of any Obfervation. 6. In its not being 
difficult to be made andadjufted, and its not being without 
indulhy anddefign put out of order, and its being prefently, 
and with all imaginable eafe rectified and again adjufted. 
7* In its not being very chargeable. Firft, For the Sights, 
They'are no other then plain Telefcopes, made with two con- 
vex GlafTes, an Object and an Eye-Glafs, of what length and 
charge flball be thought moil convenient, fixed into fquare 
Boxes or Tubes of Iron or Brafs, and having crofs Clews at 
the Focus, made with very fine Hair, or filk- Worms Clews. 
Oneof thefe is fixed upon the fide of the moveable Bar or Plate 
of the Quadrant, the Object-Glafs of which is next the Rim, 
and the Eye-Glafs is next the Center. The other of thefe is 
fixed upon the fide of the Quadrant by feveral Screws, and 
care is taken to keep it from bending or fagging. This Tube 
is made of twice the length of the former, and hath at each end 
an Object-Glafs, each of them of the fame length with the for- 
mer, and hath two Eye-Glafies in the middle, the manner of 
ordering which I fkall fliew by and by under the third 
head. 

But firft I fhall explain the manner^ fitting a Telefcope for 
a Sight. Let a a bb in the 12th. Figure reprefent a Tube,in 
which let p reprefent the part toward the Object-Glafs, 
whofe Focus is at o, and let n reprefent the Eye-Glafs, 
whofe Focus alfo is at o, let s reprefent the point, where 
the eye being placed, the whole Eye-Glafs n will beenlight- 
ned and filled with theObjeft, then make a fmall Tube about 
an inch in length, and of fuch bignefs as it will juft Aide within 
the hollow of the Tube a a bb, and crofs the Cavity of that 
flrain two very fine Hairs or filk- Worms Clews, which may 
crofs each other in the Center of the Cavity, by the means of 
which Box, the faid eroding Clews or Hairs may be moved to 
and fro, till they are exactly placed in the very Focus both of 
theObjedr-Glafs and Eye-Glafs, for if they be not there, the 
moving of the eye to and fro over the hole at s, will make the 
Threads feem to move upon the Objeds, but if they be exacl- 



iy 



(47 ) 
ly in both theaforefaid Focus's, the moving of the eye will 
not at all make the faid Threads feem to move upon the Object, 
but they will appear as. fteady and fixt to the Objeci, as if 
1 they were drained and faftned to it And though they are ex* 
ceeding final I, even as finall as the Web of a Spider or Silk- 
Worm, they will appear very big and diftinft, and much 
plainer and bigger then a Thread in the Common Sights, at 
the further end thereof, will to the naked eye, though above 
loo, nay rooo times the bignefs, which at the firft glance 
will fufficiently difcover the vaft advantage thefe kind of Sights 
have above the Common ones. Nor is this way of Sights at al 1 
confined, but may be made to diftinguifli the fmalleft part of 
the Object, defirable, even the parts appearing to the naked 
eye, under the Angle of a (ingle fecond or third of a Degree, 
Which is fome hundred of times more curious then the naked 
eye can diftinguifli, 'without the help of them, for the Telef- * ■ 
cope can be made longer, and the Eye-GIafs can be made deep- 
er, and according as the Telefcope is longer, and theEye- 
Glafs deeper, fo will the Object appear bigger, and more mi- 
nute parts be diftinguifihed, the power of the eye being in- 
creafed proportionately to the length of the 0bje6 Glafs, and 
the charge of the Eye-Glafs, and thegoodnefs of them both. 
Now as Sights this way "made,are capable of the greateft accu- 
ratenefs deferable, fo they, are fo appropriated to the eye, 
that they no ways ft rain it^for they may be fo ordered, as to 
make all thofe parts that are to bediftinguiftied, to appear to 
the eye under the Angle of 3 or 4 minutes, which moit eyes are 
able well to diftinguifli, without ufiflg too much attention or 
(training to difcover them. This is no fmall convenience, to 
one that is to make many Obfer vat ions one after another, for 
the eye by too much attention is apt to be fuddenly weary'd, 
and it doth very much harm and weaken the Sight, to endea- 
vour to diftinguifli parts fi>_ fmall, as appear ro the eye under 
the Angle of a minute, very few eyes being able to reach it at 
all, and mod: others nor without much difficulty and endea- 
vour. *Tis fur? her considerable upon his account, chat 'tis 
fitted for all kinds of Sights : For a ihon-lghted perfon, the 
Eye-Grafs ma he made to Hide a little nearer the Crofs in the 
Focus; and for an : old or decayed Sight', theEye-Glafs may be 

moved; 



(4*3 

moved a little longer or further off from the faid Crofs or Fo- 
cus • for a dim Eye, the aperture of the Objed-Glafs may be 
augmented, and the Eye-Glafs made fliallower, or of a jefs 
charge; and for a weak, tender and curious Eye, the charge 
of the Eye-Glafs may be augmented, and the aperture of the 
Objed-Glafs made lefs. And according to the feveral confti- 
tution of the Obfervators eyts^ rhe manner of Sights may be ac- 
commodated , which the other Common Sights without the 
help of Glades, are no ways capable of. 

The fecond thing wherein the perfection of this Inftrument 
confifts, is the way of making the Divifions, which I think, is 
far beyond the Common way, both for the certainty and eafe 
cfmaking, and fecondJy, for the plainnefs and certainty of ir, 
in being diftinguifhed 5 nor is it capable of lefs accuratenefs 
for meafuripg, then the Sights are for diftingu idling. And it 
excels all the Common ways of Divifion in thefe particulars : 
1. That it is made certain and not byguefs, we being not at 
all to depend upon the care, credit and diligence of the Inftni- 
ment-maker, in dividing, graving or numbring his Divifions, 
for the fame Screw makes it from end to end, as you will fee by 
and by. 2. That the Divifions are not at all difficult to be di- 
ftinguifhed, and there is no uncertainty in the Fabrick, nor 
can there be any reafon of miftake, there being nothing to be 
looked after, but the Numbers exprefled in Figures at large, 
fufficiently plain to any one that ccn read the Print of a large 
Church-Bible. It excels the Common ways thirdly, upon 
the account of its Compendium ; for whereas by tieho\ or He- 
veliuss way, »the Inftrument muft be made of 1 50 foot Radius 
at leaft, eafiiy and certainly to difcover and diitinguiflb Se- 
conds, in this way it may be made to do it within the compafs 
of 3 foot Radius. And whereas in either of their ways, even in 
an Inftrument of 1 $0 foot Radius, the Divifions are not eafiiy 
diftinguifhed and difcover'd without the help of Glafifes, in 
this way they are made fo eafie and plain, that a man cannot 
miftake, that is able by his naked eye to diftinguifh Decimals 
of an inch. Now that this is fo, as I affirm, the Reader will 
eafiiy underftand, if he confiders, firft, that the bignefsofa 
minute is hardly half an inch, in an Inftrument of 150 foot Ra- 
dins, and confequently the bignefs of a fecond is but ~ of an 

inch, 



C 49 ) 

inch, which to a good eye is but barely a vifible poirrt at the 
bed advantage, and to mod eyes Is not diftingui (liable without 
much difficulty, and to very many notat all wihout the help 
of GlaiTes. Now though Heveliu* pretends to be able to do 
much by the help of the new way oSHmnim, Verm r, or He- 
dreuty yet if he confiders what I have now faid, he wi.l be of 
much another mind, a Radius of i o foot being but a i $<h. pare 
of one of 150, and confequently every 120th. part of an inch, 
being no lefs then 1 5 whole Seconds. At lead, lam fure, he 
will be convinced that his own is not true, if he look upon 
that Specimen of it which he hath printed in his Machina Cce- 
leftu, in the Plate T. with a moderately magnifying Glafs, as 
I hinted to him before, He will further underftand the truth 
of my AfTertion, if he confiders in the next place, that by the 
help of the Screw, I am able to make the bignefs of a Minute 
as much as I pleafe 5 for fince in an lndrument of 5 foot Radi- 
us, a Degree isfomewhat better then an inch, 'tis eafie enough 
to underdand, that there may be 30 Threads of a Screw in 
the length of an inch, and confequently there will be but 2 Mi- 
nutes to fill up the whole Circle of the Index-Plate, and confe- 
quently if the Circle be 7 inches Diameter, the Circumfe- 
rence will be almod 22 inches about, and confequemly the 
bignefs of a Minute not lefs then 1 1, and the bignefs of a Se- 
cond not much lefs theryhe 5th. part of an inch. Now the 
Index-Plate e in the find and nth. Figures, fhewsexadly the 
number of Revolutions, and the Hand S in the fame Fig"r<°s, 
fhews the parts of a Revolution, and both thefe in Characters 
large and diftinft enough 5 and therefore the certainty and 
. truth of this AfTertion cannot be further doubted. 

The way then for ihefe Divifions is this : Make a Frame of a 
Quadrant of hammer'd Iron, after the manner exprefTed in the 
firft Figure, and in the Center .hereof fix or raifea hollow Cy- 
linder, whofe hollow may be about a 40th. part of its Radius, 
and vvhofe convex part may beabouta 30th ; leave this land- 
ing above the Plain of the Quadrant about £ part of the Radi- 
us, let the out-fide of this Cylinder be made as exa<2!y round 
as 'tis poflible to be turned or wrought, then make a Ruler or 
Plate, with a round hole in it at one end, turned, groun'd and 
fitted exa&ly about the above-men tion'd Cylinder, and as 

G long 



( So) 

long as you defign the Telefcope for the Sights of the Qua- 
drant', this by a Screw on the top thereof muft be kept clofe 
and fteady upon the faid Cylinder : Upon the end next the 
Limb is to be fitted aSocket or Frame with Screws, to carry 
the Screw- Frame fteady and firm, according to the contrivance 
expreft in thefirfl and i x Figures ; this Plate muft be filed or 
bended at that part of it which touches the Limb of the Qua- 
drant, fo as to lye obliquely to the Plain of the Quadrant, and 
to be parallel to the Plain of the Frame which carries the Screw, 
and upon the part beyond the Limb muft be fixt with a Screw 
k, the Frame h h h, which carries the Screw 999, and the 
Index Plate tt ; the contrivance of this Frame hh, is to 
keep the Screw 999 clofe againft , and very fteady to the 
Limb of the Quadrant, and Is moved to and fro upon the 
Limb of the Quadrant b b b, by the help of the Screw turn- 
ing upon and againft the edge of the Quadrant 3 and this Screw 
by reafon of its diftance from the center and eye, (the reafon 
of the placing of which in that place you will underhand by 
and by) being too far off to be reached by the hand, is 
turned by a fmallRod of Iron, 000 in the firft and rr Fi- 
gures lying by the fide of the Ruler or Plate, which hath a 
fmall Wheel q q, at the end next the Limb, by which the 
Screw is turn'd round with it, and hath a fmall Handle or 
Windle p p next the Center, by which it is made convenient 
to be fo turned round. Upon the tnA of the above- men tion'd 
Screw- Frame h h, is fixed a round Plate 1 1, which is divided 
into t, 2, 3, 4, or $ hundred equal parts, according as it is in 
bignefs, and as it fhallbe thought convenient, which Divifi- 
ons are numbred and marked accordingly, ferving to flhew 
what part of a Revolution is made of the aforefaid Screw ; for 
the end of the Screw 999 coming out through the middle 
thereof, and a Hand 8 being faftned upon the faid end, every 
turn of the Screw doth make a Revolution of the Index upon 
the faid Plate ; and confequently the motion of the arm made 
by one turn of the Screw, is actually and fenfibly divided into 
r, 2, 3, 4, or 5 hundred equal parts, which is fo exceeding 
exatf, and withal fo Mathematically and Mechanically true, 
that 'tis hardly to be equallized by any other way of proceed- 
ing- This Defcription will be much better underfrocd by 

the 



(St) 

ihe Explication of the Figure* and the feveral parts there- 
of. 

Let aaaaa, &c* reprefent the Frame of the Quadranc, 
confiding of 5 Bars, radiating from the Center, fteadyed all 
of them by a Quadrantal Limb, and a ftraight fubtending 
Chord Bar; this whole Frame is to be made of very good 
Iron, partly welded and partly fodered together with Brafs ; 
the breadth of the Bars may keep the fame Proportions ex- 
prefs'd in the Figure, and the thicknefs may be about 1 §0 part 
of the Radius in large Inftrumems. In the Center of this, out 
of the fo lid Bar, istoberaifedaCylinder, as d d, expreffed 
above more plainly in the 2d. Figure 5 the out-fide of this Cy- 
linder is to be turned and wrought, as Founders do their 
Stopcocks, as exa&ly as poflibly it can be, and the end of 
the Iron Plate or moveable arm cccc, fliaped as is expreffed 
in the 3d. and firft Figure, muft be bored and wrought upon it 
very well , fo as they may turn exaftly true , evenly and 
fmoothly, without any manner of flicking or fhaking, which a 
good Workman will eafily perform. This arm being put on 
the Cylinder, is fcrewed down faftby the help of a Screw- 
Plate, expreffed in the 4th. and firft Figures by e e, which 
hath two notches in it ff, by means whereof a Handle gg in 
the 6th. Figure, doth readily fcrew and unfcrew it, as there 
is occafion. Between this fcrew J d Plate and the hole of the 
Plate cccc, is a thin Brafs Plate, let on upon an 8 fided part 
of the Cylinder, that fo the turning of the Plate cccc, may 
not have any power to unfcrew the Plate ee, which otherwife 
it is very apt to do. Why this Center is thus made, and a hole 
left in the middle thereof, you will fhortly underftand more 
plainly* Upon the Iron Limb of the Quadrant laft menti- 
on'd, is fcrew'd and rivetted a Limb of fine Brafs, firft caft 
into that fhape , and then very well hammer-hardned and 
filed, reprefented in the Figure by bbbb: This, as I faid, 
by many holes drilled through the Iron and the Brafs, is fcrew- 
ed and rivetted upon the iron Limb, fo as about half an inch in 
a Quadrant of 5 foot Radius doth over-hang the iron Limb, 
and the ends thereof extend a confiderable deal longer then the 
Quadrant, the reafon and ufe of which you will by and by un- 
derftand, when I give the Defer ipt ion of the Screw-Frame. 

G 2 Th; 



The edge of this Brafs Limb muft be, by the help of the Plate 
c c c c, and a File or Plain, cut very exaft^y rounds to an- 
fwer the Center of the Quadrant, and the upper fide thereof 
muft be plained exattly fmooth and flat, upon which Plain-fide 
the Loop-holed Plate c c c c mull: move, as is vifible in the 
Figure. This Plate at ii muft be wrenched or wreithed, fo 
that the Plain thereof muft (land parallel to the Plain of the 
Index- Frame, and by the wreithingof it at i i, as aforefaid, 
there is room left for the Screw to lye obliquely, without the 
Screws touching the aforefaid Plate , or grating againft it* 
, The reafon why I put the Screw obliquely to the Plain of the 
Quadrant is, that that part of the Thread which touchetb the 
edge of the Limb, may be exadly at right Angles, or perpen- 
dicular to that Plain, and confequently that the Teeth upon 
the faid edge, maylikewife beexadly crofs or perpendicular 
alfo, and confequently that no bending of the Rule c c c c, 
(to the end of which the Frame of the Screw is faftned) may at 
all vary the Angle, nor any unequal thicknefs in the Limb of 
the Quadrant, but that the turning only of the Screw fhall 
produce a variation, and that exactly proportionate to the 
number of Revolutions, and the parts thereof, fliew'd by the 
Index. 

The way to know exa&ly what the obliquity of the Screw 
ought to be, to make the Teeth upon the Limb perpendicu- 
lar, is to number how many Threads of the Screw there are in 
a known length, and what the Compafs of the faid Screw, or 
the Cylinder out of which it is made is, and multiplying the 
faid Compafs by the number of Revolutions into a Product, 
ihe Proportions of that Product to the known length, will give 
the obliquity of the Screw, the Produft being the Radius, 
and the known length the Tangent of obliquity, thus; Sup- 
pofe in the length of 4 inches, there be 83 Threads of the 
Screw, and that the Compafs of the Cylinder of the Screw be 
\p2_ Centefms of an inch, 1 multiply the J?2 by 83, the num- 
ber of Revolutions, and itgiveth me 76^ that is 76 inches, 
and 36 Centefms of an inch, making this Product the Radius, 
and the known lengthy viz, 4 inches, the Tangent of the ob- 
liquity of the Thread of the Screw to the Axis thereof, orof 
the Axis of the Screw to the Plain of the Quadrant. The de- 

monflration 



(53) 
monftration of this is fo plain, that I need not infift upon it,., 
for the length of the Thread of the Screw is the Secant, the 
Compafs of the Cylinder is the Radius, and the bignefs of the 
Thread, or the Diftance bet ween two Threads, is the Tangent, 
in a right angled Triangle, and the Screw isfucharight ang- 
led Triangle, wound about a Cylinder, putting the Tangent 
thereof parallel to the Axis of the Cylinder, and confequent- 
ly in the Mechanical cryal of thefe Proportions, the more 
Threads are taken to make that comparison or meafurement, 
the more exact is the inclination found. The confideration of 
which doth plainly fliew, how exacl a way of Divifion this by 
the help of the Screw is, for the whole Quadrant is thereby 
refolved into one grand Diagonal, the fame with the Triangle, 
the length of the Thread upon the Compafs of the Cylinder be- 
ing the Diagonal, and the Diftance of the two ends of thofe 
Threads, in a Line parallel to the Axis, being the fpace to be 
divided by it, and confequently by augmenting the bignefs or 
Compafs of the Cylinder, and' diminifhing the Thread, you 
may augment the Diagonal in any Proportion affigned. Or by 
making the Hand or Index upon the end thereof, of double, 
treble, quadruple, decuple, &c. of thefemi-Diameterof the 
Cylinder, out of which the Screw is made, you may dupli- 
cate, triplicate, quadruplicate, decuplicate, &c. the faid 
length of the Diagonal, in Proportion to the fpace to be di- 
vided. 

The next thing then to be defcribed is the Screw-Frame, 
made of Iron, much of the fhape reprefented by h h h, in the 
firft and i r Figures : This Frame, by the help of a Screw 
through the aforefaid Plate, whofe head is exprefled by the 
round head k, is fixed on to the long Plate from the center, 
and by the help of the Screw 1, is forced and kept down very 
clofe, upon the edge of the Limb of the Quadrant ; the Frame 
hath 4 Collers for the Screw-Pin to run againft, which are in- 
deed but half Collers, fervingonly to keep the Screw fteady ; 
two of thefe are made with moftcare, marked with mm, in 
the nth. Figure againft mi, doth reft the Shoulder of the 
Screw- Pin 3, which is kept clofe home againft it, by the Cy- 
linder gg, in the 10 and n Figures ; the fharp Conical 
Point of this Screw 9 9, goeth into the Conical hole, at the 

end 



(54) 

<nd of. the faid Cylinder gg g. Thefliape of this Cylinder, 
and the Screw by which ic is forced againft the end of the 
Screw 99,isreprefented in the roth. Figure; 7 inthe9th.Fi- 
gure reprefents the Conical Point ; 3 the place lying againft 
the Colier mi; 6 the Screw that moves upon the edge of the 
Limb of the Quadrant; 5 the Nut or Pinnion by which the 
Screw is turn'd by a Rod from the Center, expreft alone in the 
8 th. Figure, but the manner how it lyes in the Frame, is ex- 
preft by p p o o in Fig. 1.000 reprefentingthe Rod;p p the 
Handle by which it is turned ; qq the Nut or Pinnion that 
curneth the Pinnion 5 of the Screw; s r the Col lers or Holes 
that hold it fad to the moveable Plate or arm of the Quadrant ; 
ss reprefenteth two fmall pieces that clip the edge of the 
Limb, and ferve to keep the Screw- Frame fteadyand true in 
its oblique pofture, and move equally on the Limb, byaftrong 
fpringing of one fide of it ; 1 1 reprefenteth the Index-Plate, 
which is divided into what number of parts are thought necef- 
fary, 1, 2, 3, 4, or 5 hundred parts, according to the bignefs 
of the Thread of the Screw at 6, a greater Thread requiringa 
more minute Divifion, and a fmaller Thread requiring a more 
grofs. Thefe Divifions are pointed at by the Index 8 at the 
end of the Screw, and the number of Revolutions or Threads 
•are marked on the Limb of the Quadrant, and pointed at by 
the Tongue e e, upon the which is fanned a fmall Pin f, ferv- 
ing to carry a Lens over the Point of the Tongue, which 
maketh the number of Threads appear more plain and big: 
The manner of doing which upon the Frame of the Screw, is 
fo eafie, that I fihaJl not fpend more time in the Explication 
thereof, and the manner of >making the whole Inftrument, will 
be eafie enough to any ingenious Workman $ but if any perfon 
defire one of them to be made, without troubling himfelf to 
direcland overfee a Workman, he may imploy Mr. fompon, 
a Watchmaker in Water-ham near Fleetfireet ; this perfon f re- 
commend, as having imploy *d him to make that which I have* 
whereby he hath' feen and experienced the Difficulties that do 
occur therein,, f and finding him to be; very careful and curious 
to obferve and follow Directions, and tocompleat and per- 
fect his Work, fo as to make ic accurate and fit for ufe. 

By 



< SO 

By the help of thefe Indices, 'twill be eafie and plain to fee 
how many Revolutions of the Screw, and what parts of a Re- 
volution make a Quadrant of a Circle, and confequently 'twill 
be eafie to make a fmall Table, which fhall ihew what parts of 
a Quadrant, divided into Degrees, Minutes and Seconds, will 
be defigned by the Revolutions, and parts of the Revolutions 
of the Screw. As for inftance, If I find that i £00 Revoluti- 
ons and [912 make a Quadrant, then 1 7I788 Revolutions make 
a Degree, and \2p6 Millefms of a Revolution make a Minute, 
and about 5 Millefms make a Second, thence 'twill be eafie to 
find (if you obferve ) an Angle to contain 294I3JI, that is, 
294 Revolutions, and 358 Millefms of a Revolution, tljat the 
Content of that Angle in Degrees , Minutes and Seconds, 
is 16 Degrees, 32 Minutes,- and 47 Seconds, which is plain 
enough, and much lefs fubjefl: to miftake, then the common 
way made ufe of. I fliall therefore proceed to 

The third particular, wherein this rnfrrument excels alio- 
thers,and that,is,That oneObfervator with a fingle glance of his 
eye,at the fame moment doth diitinctly fee,that both theSights of 
the Inftrument are exa&ly directed to the defired Points of the 
twoObjefts, and this, though they be removed by never {0 
great an Angle, nay, though they are oppofite to each other 
dire&ly in a Line* This, I queftion not, will by all that 
know any thing of Instruments, or celeftial Obfervations, 
be accounted one of the grcateft helps to fuchObfervations, 
that was ever found out. For whereas other Inftruments re- 
quire two Obfervators, for taking a Difrance in the Heavens, 
and Ticho generally made ufe of four, amongfi: which there 
was neceflfary fo unanimous a concurrence in their readinefs and 
certainty, that the failure of any one fpoyl'd all thereit, and 
made the Obfervation become uncertain and of no ufe; and 
fuch Inftruments as were contrived for one Obfervator^ were 
accorapany'd with fo great difficulty, in the adjufting to both 
the Objects, being both in a continual and fwift motion, and 
but one to be feen at once, that they were generally left ofFand 
dif-ufed, there being fo vaft a trouble and fatigue of looking 
now upon one, then upon another, by many repeated tryals, 
and fo many new fettings of the Inftrument to the Objects in 
motion > before the Sights could be adjufted, befides the 

great 



( sO 

great uncertainty at the beft, of feveral Minutes of the truth 
I n this way, the Obfervator has no farther trouble, then firrV 
to fee the Plain of the Quadrant in the Plain of the Obje&s, 
and by the Screw to move the arm of his Inftrument, till he 
perceive both the Obje&s to touch each other, in thofe Points 
he would meafure the Difta nee ber ween. That this is fo, he 
will eafily perceive, when he understands the method of fo 
adapting two Telefcopes, that by looking in at one fmall hole 
in the fide of one of them, he will be able to fee both thofe 
Objects diftinftly to which they are directed, how much 
foever feparated. The way then of doing it is in fliorc 
this. 

Joyn them together at one end, by a hollow Joynt that has 
a hole through it, about ± of the hollow of the Tubes, prepare 
two fquare Tubes of Wood, Brafs, Tron, &c. of what length 
you pleafe, and direftly againft the Center of this hole in the 
Joynt, make a fmall hole, about the bignefs of the blacked 
part or pupil of the eye, fo as the eye looking in at that hole, 
may fee perpendicularly into the lower Tube, thenobliquely 
place two pieces of reflecting Metal, very well and truely po- 
liflit, fo as to reflect the Axis of both thofe Tubes, perpendi- 
cular or ac right Angles, which is by fixing the Plain of the 
Plates, inclined to the faid Axis, in an Angle of 45 Degrees, 
let the upper reflex Plate reach from the upper fids of the Tube, 
fo low as to touch the Axis or middle of the Tube, and let the 
lower extend over the whole Tube, from the top to the bot- 
tom, and from one fide to the other. Thefe will be known to 
be duely placed, if looking in at the fmall hole againft the 
Center of the Joynt, the two round holes of the Tube do ap- 
pear to the eye to coallefce into one, and that the eye fees di- 
rectly through rhe lengths of them both alike. Then into 
thefe Tubes fit two Telefcopes, with convex Eye-GlafTes, and 
crofs Threads for Sights in their Foci, that they may be both 
of them at due diftance from the eye, looking in ac the fide- 
hole, then opening thofe Tubes upon the faid joynt to any 
Angle, and looking in at the fide hole, you fhall plainly di- 
ftinguifh at once both the Objects, that are brought into the 
Tubes dire&iy, and refle&ed up to the eye. 

Thatthistnaybe the plainer underltood, I fhall add a '■De- 
lineation thereof mflmo. Let 






(57) 

Let a a bb ino]er2th. Figure reprefent the upper Tube* 
and cccc the lower Tube, and let d d reprefenc that part 
of the joynt, which belongs to the lower Tube, at one end, 
by which they are joyn'd together, and can be open'd in the 
manner of a Sector. Let i repre fen t the hollow or center of 
this Joynt, which communicates the Cavities of the two Tubes, 
Let e e reprefent that part of the faid Joynt which belongs to 
the upper Tube, being only a hole through the lower fide, 
big enough to incompafs the Cylinder d d of the lower Tube ; 
and ]^t rr reprefent a Plate fcrewM or pinn'd on, to keep 
the parts of the Joynt together inftead ofrivetting. Let s re- 
prefent the hole in the fide, by which the Eye h is to look in, 
and f the reflex Mettal in the upper Tube, reaching only half 
way the Tube, and gg the reflex Mettal in the under Tube, 
reaching over the whole Cavity 5 then will n o and p repre-. 
fent the Eye-Glafs, Sight-Threads, and Objed-Glafs of the 
upper Tube, and k 1 and m the fame parts in, the lower, and 
whatever Ang ! e the Tubes make to each other, whilfl they 
open upon the before-mention'd Joynt, the Eye h looking in 
at s, will fee directly by the Axis of them both, and fee the 
Sight-Threads diftin&ly eroding the Points of the Objects, 
whofe Diftancesare to be meafured* 

Thefe being thus explained, I fuppofe, it will be no diffi- 
cult matter for any man to conceive, how thefe may be apply 'd 
to the above-defcribed Quadrant $ for 'tis but fuppofing cc, 
the upper fide of the under Tube in this Figure, to reprefent 
apap, the fixt fide arm of the Quadrant, and d d the Joynt of 
this, to reprefent dd the Joynt of the Quadrant, and bb the 
under fide of the upper Tube, to reprefent ccc the move- 
able arm of the Quadrant, and applying two Tubes to thefe 
parts, and fitting them with reflecting Plates, Eye-Glaffes, 
Sight-Threads , and Objeft-GlafTes , at due Diftances , the 
whole will be performed. 

Thefe Tubes thus fitted, will ferve to take any Angle lefs 
then a Quadrant, to what exactnefs i defired, but for bigger 
Angles, the Contrivance muft be fomewhat varied, the De- 
fcription of which I fhall now add. 

Let either of the two Tubes for the Sights, be made of dou- 
ble the length of the other, that is, let it be as long behind the 

H Center 



( 5«) 

Center as before it, and make the Reflex-ftlafs, that it may 
be turned round, and reflect the Ray exa&ly backwards, as 
before it did forward, then fix into this other half of the Tube 
aTelefcope-Sight, in all things fitted, adjufted, andlikethe 
other two, then adjuft them, that they may look forwards and 
backwards in the fame like, which being done, the Reader 
will eafily underftand how any Angle may be taken, even to 
the extent of two right ones : For 'tis plain enough, that the 
two Tubes I firft defcribed, apply 'd to the Quadrant, will 
meafure any Angle to a Quadrant or right Angle j and 'twill 
be as eafie to underftand, how by the help of the Reverfe-Tube, 
any Angle between a Quadrant and two right Angles may be 
meafured. 

To make this a little plainer to the Reader, let ccccc in 
the 1 2th. Figure reprefent the under Tube or fixed Sight, 
s the hole or Eye- cell, tr a round piece carrying the reflex 
Mettal g g 5 this is made to turn round,and the reflecting Mettal 
g g being fixed to it within the Tube , is carried round 
alfo with it. Let siklmx reprefent the Ray palling 
forwards by the Eye-Glafs, Thread-Sight, and Objetf-Glafs 5 
then this round piece t r being turned and made rt, as in the 
13th. Figure, is reprefented, and with it the reflecting Mettal 
g g, here marked q q, being turned alfo ; the Line s q k 1 m y 
will reprefent the Ray reflected, and pafling backwards by the 
reftex-Mettal q q, Eye-GJafs k, Thread-Sight 1, and Objed- 
Glafs y. 

The meafure of the Angle is found by the fame Apparatus or 
Screw-Plate; forasmuch as the Screw-Plate would (he w the 
Angle lefs then a Quadrant, if the fore- part of the Tube were 
ufed, by fo much is the Angle more then a Quadrant, if the 
reverfe or back part of the Tube be ufed ; and the fame reafon 
of the accuratenefs and certainty for the one, is good for the 
other, without being lyableto any manner of Objection or In- 
convenience* 

It remains therefore now only to (hew, Firft, How thefe 
two Perfpe&ive or Telefcope Sights, placed within the fame 
Tube, may be made to look exa&ly forwards or backwards in 
the fame Line. And fecondly, How they fiiall be adjufted to 
the Telefcope, fixt upon the moveable arm of the Quadrant, 

To 



■'(59) 

fo as to know when the Divifion- Angle begins, and when they 
are opened to a Quadrant, right Angle, or 90 Degrees j for 
unlefs thefe be afcertain'd, and fixt to as great a meafure of ac- 
curatenefs, as the contrivance of the Screw is capable of divi- 
ding, or the Telefcope-Sights are capable of diftinguiflbing, or 
the Perpendicularity afcertain'd , all the pains, care, in- 
dustry, and curioficy, beftow'd about the other, are of no 
ufe. 

Firft then, For fixing the Thread-Sights of the twoTelef* 
copes, within the fame Tube, fo as to look direftly forward 
and backwards, care muft be taken, that every one of the four 
GlafTes, that is rqfay, the two Object-Glafles, and the two 
Eye-GlafTes, muft be fo fteadily and fecurely fixt into the 
Tube, that they cannot by any means be ftirr'd or removed ; 
the manner of doing which, I fuppofe, fo exceeding eafie, 
that I need not fpend time in defchbing a way to do It. Next, 
Sufficient care muft be taken of the ftiffnefs of the Tubes, that 
they may not warp or bend. Thirdly, One of the Thread- 
Sights muft be fixt as firmly and fecurely as the GlafTes, and fo, 
that the croffing of the Threads may be, as near as poftible, in 
the Axis of the Object and Eye-Glafs, the other Thread-Sight 
muft be left free, till by feverai tryals it be found to ftand ex- 
asftly in the fame Line with the firft 5 the manner of doing 
which, I (hall now defcribe* 

There being two Threads which crofs each other, the one 
Perpendicular and the other Horizontal, care muft be taken,; 
that both thefe lye exadly in the fame Lines with the Horizon- 
tal and Perpendicular Threads in the other Sights ; and in 
order thereunto, there muft be two Frames of Brafs, repre- 
fented in the 29 and 30 Figures of the 2d. plate, of the big- 
nefs of the hollow of the Tube ; thefe muft have groves made 
in the Tube fit to receive them, in which they may by the help 
of Screws bemoved, and made to Aide to and fro' % as there is 
occafion, for their adjufting. Next, They muft lye fo clofe 
together, that the Hairs may touch each other. And thirdly, 
They muft crofs exa&Iy in the Focus of the Object and Eye- 
Glafs. One of thefe Frames muft carry the Perpendicular 
Thread, and by a Screw in the (ide of the Tube, muft be move- 
able to the right or left fide, as there is occafion ; the other 

H 2 Frame 



(6o) 

Frame muft carry the Horizontal Thread, and by a Screw in 
the top of the Tube, mull be made to rife or fall in the Tube, 
as there is need. The Mechanical Fabrick of which is fo eafie, 
that , I hope , I need not fpend time in the further De- 
fcription thereof, but refer the Reader to the 29 and 30 Fi- 
gures. 

Thefe things being thus done, from the top of fomeTurrer, 
or any other Station, where two oppofite places at a confide- 
. rablediftance, as half a mile, or a mile or two, can be plainly 
feen, find out two Points, which, at the firft looking through 
your Glades, you find to be fhewn out by the CroiTes of the 
Thread- Sights, then note thofe Points very diligently, that 
you may be fure to find them and know them again, when you 
have removed the GlaiTes ; this done, turn the ends of the 
Tube, and ( if you were looking Eaft wards and We ft wards ) 
turn that part towards the Eaft which before looked Weft- 
wards, and vice verfd, and find out the two Points you faw in 
the former Obfervation, then directing that part that hath the 
fixt Threads, to the Point that was feen before by the move- 
able Threads, find out the other Point, which you will be fure 
to fee within the compafs of your Eye-Glafs, and obferve how- 
far the crofs Threads are now removed from it, either North- 
wards or Southwards, upwards or downwards, then, as near 
as you can, by your judgement halfthat Difference, and by the 
Screws move the Frames, that the Threads may frand in the 
middle between the two Points, then take notice again of the 
Points fhewnby the Threads, and turn the Tube again: Do 
this fo many times, till you find upon converting the Tubes, 
that you fee the fame Points to be marked by the CroiTes of the 
Thread-Sights, with which end foever you look on them, and 
then the Tube will be exacl: and fit for ufe. . 

Thereafon of this adjufting will be fuffici«ntly plain, to 
any one that fliall confider the 14th. Figure: Where let v re- 
prefent the middle of the Tube tub, or the place of the Eye, 
and let w reprefent the Object feen Weftwards, and e the 
Objeft Eaftwards, at the fir ft view ;. then keeping the middle 
of the Tube exactly upon the fame Point u, turn the end of 
the Tut^ t towards the Eaft , and the end b towards the 
Weft, .and find out firft theEafternObjeft e, and finding the 

other 



C 61 ) 
other Crofs to direct now to the Point* p, tnd not to w, di- 
vide the DiStance between the Point w, and the Point p, as 
exa&ly as.you can, in half, which if you chance to hit exactly 
at firfr, it will be the middle Point w, but if you do not, but 
you reclifie it only to r, then by the next turning of your Tube 
you will find s, where you mult, again re&i fie to half the Dif- 
ference between s and r ; now the Difference being grown 
yet lefs, you will a 3d. or 4th. time fet it foexa&ly, as to fee 
the Points m and e, which lye in the ftraight Line with the 
Center of the double Tube. 

The 4th. thing wherein this Quadrant exceeds the Common, 
is for its accuratenefs for taking Altitudes ; and this is done by 
the help of a Water- Level, for adju (ting the exaft Perpendi- 
cularity thereof* This Level may be made and fixed fo exact- 
ly, that any Obfervator may be fure of the Level of his Inftru- 
ment to a Second or two. The Level it feif is nothing but a 
fliort Tube of Glafs, about 6 or 8 inches long, Hermetically 
fealed at each end, and filled with a Liquor that will not freeze 
nor grow foul with {landing. 

TheGlafs, as near as can be gotten, fhould be Cylindrical 
and ftraight, it being the better the nearer it be to a ftraight, 
provided it have a fenfible bending or f welling in the middle, 
the gibbous part of which fhould be fet upwards, and a pro- 
per Cell and Box made for it of Brafs. 

This Glafs is to be filled aimoft full of diftill'd Water, to 
which about a 3d. pan of good Aqua-fortisor fpirit of Niter 
hath been put, to keep the fame from freezing, and alfo from 
growing foul, then carefully fealed up Hermetically 3 and pla- 
ced in its Box of Brafs, and with hard Cement fixed into the 
fame, which by Screws is fixed to that fide of the Quadrant, 
that is to lye Horizontal. 

The Brafs Box being thus fixed to the right fide of the long 
fixt Tube ap ap ap, and underneath the Quad ran t,- fo as not 
to hinder the free movement of the arm ccc, as at x x 5 the 
next thing to be done, is by it to fet the Quadrant truly Hori- 
zontal, which is thus performed. 

Setting the fide a p ap a p Horizontal, and the Limb of 
the Quadrant upwards, and looking in at the Center, take 
notice of two Objefts in the Horizon oppofite to each other, 

irvc - 



>2\ 



obferve the limits of the bubble qf Air on the top of the Li- 
quor, on each fide of the. middle or the Level, and make a 
mark, then turning the ends of the Quadrant, fet it, till the 
ends of the bubble ftand as in the former Obfervation ;. then 
look again at thofe Objects in the Horizon, and find what the 
difference is between thefe oppofite Objects, and thofe in the 
former Obfervation ; then halve the difference between them as 
near as you can, and by your eye fee the Sights to the middle 
between them, by inclining the Quadrant, then by the Screw- 
that rectifies the Level, fet the Glafs-Level fo, that the ends of 
the bubble may be equally diftant from the middle, and con- 
vert the Quadrant again, and fee if the ends of the bubble 
Handing at the fame marks, the two oppofite Telefcope-Sights 
do fee the fame Obje&s, for if fo, you are affured of the per- 
fect Horizontality of the Sights, upon the fixt arm of a p ap ; 
but if you do not find it to dire& to the fame Obje&s, 
continue examining and converting-, till> you find it per- 
fect 

Now this way of Perpendicular being fubj eel: to the incon- 
venience of heat and cold, which doth rarifie and condenfe the 
Liquor, and co"nfequently make the bubble of Air lefsor 
more, care muft be taken, to mark all the varieties of thofe 
kinds of the bubble, that are caufed by the degrees of heat and 
cold, which you may thus eafily effecT:. 

Reduce the Liquor in the Tube of the 24th. Figure, by the 
help of Ice and Salt, to as great a degree of cold as you can, 
then by the method newl.y directed, fet the Quadrant Hori- 
zontal, and mark the two ends of the bubble with 44, then by 
gently applying heat to the ambient Air, warm likewife the 
Water, and obferve. the expanfion thereof at both its ends, 
and mark them on the Glafs with the point of a Diamanr, as 
33. 22. n.oo, which being done, it will be exceeding eafie 
at any time, to adjuit the Quadrant to any accuratenejs dtd- 
red, by being careful to fee, that the two ends of the bubble 
beproportionably extended, as to 00. 11. 22. 33.44, ^r. 
or to any intermediate fpace. 

The Contrivance of feftening and adjiuKng.chis, Leveko the 
Quadrant or or-her- [nftrument, wi-ilbe very eafily understood, 
byd:e Delineation thereofin the 24th, Figure. . 

Let 



C 63 ) 

Let aaaa reprefent'the Frame or Plate of Brafs, which 
by four Screws dd.dd, h .fixed.to the .Tube ,. as before. 
This Plate hath 4 upright. Cheeks,- bb, cc, between which 
the Brafs Box ee e e, (mto. which the Cylindrical Glafs-Lc- 
vel ff, is fixed with hard Cement) is held fteady, without 
any manner of fhaking. This Brafs Box, at the end ofit near 
the right hand, hath 2 Pevots, which are fitted exactly into 
2 final I holes in the Cheeks cc, and at the other end next the 
left hand, hath a fiflali Screw- Pin g, which holds it -downfaft 
to the bottom Plate, and keeps it from riling out from between 
the Cheeks bb, which a very. firong Spring lying underneath 
it, between the Plate a a, and the Box ee, would otherwife 
force it to do, By this Screw the Level is to be adjufied to 
the Sights of the Quadrant, by the way I juft now defcribed, 
and being once thus adjufred and fixed, 'tis not eafily put out 
of order, without moving or altering the Screw g, which 
may eafily be prevented by 100 Contrivances. 

TheReafonof theaecuratenefis of this- kind of Level, will 
be eafily difcover'd, if we confider, that the upper part of the 
Tube being very near to a ftraight Line, is confequently ei* 
therapartof a Circle of a very great Radius, orof fo me ir- 
regular Curve, very near of the fame nature with a Circle, as 
to this bufinefs of Levelling, and confequently a Degree of the 
fame will be proportionably large, and the flexure of the Tube 
may be made of a Curve of fo large a Radius^ that every Se- 
cond of Inclination may caufe a change in the Level of a very 
fenfible length* 

This can hardly be performed by the ordinary way of 
Plumbets, without hanging from a vaft height, which is not 
pra&icably to be performed, without almoft infinite trouble, 
expence and difficulty, and when done, can be of no uCc in 
the World, as any one will grant, that confiders the vaft Appa- 
ratus that is requifite to obviate the great unfteadinefs of 
Buildings, the motion of the Air, and amulti fade of other in- 
cumbrances. 

Now the Curvature this way made may be a portion of a 
Sphere of 1000 foot Radius, or more, if it be defired, and 
confequently a Minute of the fame will not be lefs then -^ of 
afoot, and every Second will be almoft half a Centefm of ^ 

foot, 



(64) 

foot, which is fufficiently diftingui&ablc to the naked eye. 
So if the'GIafs Cylinder be 9 inches long, it may contain two 
whole Minnies of fuch a Circle between f and f, and one be- 
tween 4 and 4, and confequently the faid Glafs may be fee Ho- 
rizontal to the certainty of a Second, which is hardly to be 
afcertain'd any other way. 

But there remains yet one great Difficulty, how to be able 
to make fuch a Curviture, for though the thing be true in the- 
ory, yet is it not without fome trouble, put in practice. Ve- 
ry few Glafs Canes are fo conveniently bent, as is defirable, 
and 'tis as difficult to find them true ftraight. 

To prevent this. If Glafs Canes be ufed, there muft be much 
care taken, and many tryals made, for the finding what pieces, 
and what fide of thofe pieces will be raoft fit for this purpofe, 
for our Glafs-Houfe Workmen know not yet a way, certainly 
to draw them of this or that curviture or ftraightnefs, nor are 
they eafily ground into a ftraightnefs or curviture by the Glafs- 
grinder afterwards, though that can be done with fome trou- 
ble. But diligence and tryal will quickly find fome piece or 
other, that will be fufficiently exaft for any tryal, among 
thofe which are only drawn at the Glafs-Houfe, I made ufe of 
one of another form, fuch as isdefcribed in the 25th. Figure, 
which I found to do exceeding well, the dark part reprefent- 
ing the Water, and the lighter part the Air. This was made 
of two GlaiTes, drawn in diftinCl Pipes at the GJafs-Houfe, 
but joyn'd together in the Lamp, and the upper part of the 
larger or under Tube, was incurvated with its convexity ' 
downwards, fo that the Wacer touched the middle parr, and 
the bubbles of Air at each end thereof, communicated toge- 
ther by the fmall Pipe above. I tryedalfo another way, by 
which I was more certain of the truth of the Curvity, and 
could make the Curvity of a greater Circle : This was by a 
long piece of a Looking-Glafs- Plate, ground very fmooth and 
pohfhed, which by the help of Screws I bent upon the circu- 
lar edges of a brafs prifmatical Box, and cemented the fame 
very tight, with hard and fofc Cement; this Plate had a hol- 
low Channel ground in it the length thereof, which ferv'd to 
keep the bubble in the middle. By this means, 'tis not diffi- 
cult to bend fuch a Plate, into the Curviture of a Circle of 50, 

60, 



60, roo, T600 foot Radius, and the BrafsBox can eafify be 
made to fill or empty, as there fhall be occafion fortheufe 
thereof, Co that the Bubble may be at any time left, of whac 
bignefs fhall be delired. It will be convenient alia to varniOi 
the in-fideof this Brafs Box with Lacker- Varnifh, very thick 
and clofe, both to keep it from rutting, and-alfo to preferveit 
from being corroded by Aqua-fortis, whenfoever there fhall 
be occafion to put it in, for the cleahfing the inward tarmfii 
and foulnefs of the Glafs-Plate, This Curvity of the upper 
fide of the Level may be made, by grinding the under fide of 
fuch a long Plate of Looking Glafs, upon a Convex G!afs-Tool 
of 50, 60, 100, 1000 foot Radius, and polifhing the fame ac- 
cordingly of that Figure : The Curvity of the faid Plate is ex- 
prefs'd in the 26th. Figure. Now what by this way may be 
done with Water and Bubbles of Air, the fame may be done. 
with the fame GJafTes turned upfide-down, by the help of an 
exactly round and polilht Cylinder or Globule of Glafs, Chry- 
fral, Cornelian, Agate, or other exceedingly hard and clofe 
Stone, after the manner reprefented in the 27th. Figure, for 
the Ball or Cylinder will naturally roll to the loweft part of 
the Concavity, and there ftand. But in the doing of this,great 
care mud be taken, that the Globule be exactly round and po- 
hfht, and that the Concavity of the Plate be as fmooth and well 
polilht, and that they be both very clean and free from dufr, 
otherw r ife the Cylinder or Globule will be apt to (land in a 
place where it fhould not, and confeqtiently produce conside- 
rable errors. 

And here I cannot omit to take notice of a very curious Le- 
vel, invented bySr. Chr. Wren> for the taking the Horizon 
every way in a Circle. Which is done by a largeConcave, 
ground and polilht on a very large Sphere, and the Limb of it 
ground and polilht on a flat, for by placing the fame Horizon- 
tal, and rectifying it by a final 1 quantity of Quick-filver, pour- 
ed into the Concavity thereof, 'twill beeafie, by looking by 
the flat polilht Limb, to difcover the true Horizon. The only 
inconvenience I find in it is,that the ^ hath fome kind of flick- 
ing to the Glafs, but a fmall Chrylhl Bowl, I fuppofe, may re- 
medy that inconvenience, and make it fit for ufe. 

The 5th. thing wherein this fnftrument is made to excell 

■I others, 



C .«« ) 

others, isin its eafineiTesjto be.adjufted-tatheObjefts, and in 
this, that being once adjufted, the whole Infhument is fo or- 
dered, as chat it will remain conftant to thofe Obje&s, though 
they are moved. The want of this is fo great an inconvenience, 
in all other Instruments hitherto made ufeof, that almoft all 
Obfervations have been thereby vitiated. And Bevelim, to 
prevent and obviate this, hath found out many Contrivances, 
but they are fuch, as though they do it in parr, yet 'tis but in 
part, and that with much trouble and inconvenience. I need 
not fpend time to fhew, how many inconveniences his way by 
4 feveral Hand-Screws, to be managed by 2 Obfervators at the 
leaft, is fubjecl to 5 they are indeed fo many and fo great, that 
icwas not without very good reafon, that he fo often appeals 
to experience, for the truth is, there was great need of long 
pradice and much experience, to be able to make an Obfer va« 
cionin that way well, the removal of every one of thofe Screws, 
having an influence upon every one of the other, fo as no Screw 
could be turned, but the whole Inftrument was put out of its 
due fituation, and both theObjecls being continually in moti- 
on,the wholelnftrument was to be re&itYd every momenr.There 
was therefore neceffary fo great a judgement and dexterity, to 
manage every one of thofe Screws, that without an acquired 
habitude and handinefs by long practice and experience, no- 
thingcould be done to any certainty, nay, not even to that lit- 
tle accuratenefs that the common Sights are able to reach. But 
this, though it were a very great unhappinefs to Bevelim, that 
he was not furnifiied with better Contrivances, yet it no ways 
tends to his difpraife, for his moft extraordinary and indefa- 
tigable care, pains and indu/try, is fo much the more to be ad- . 
nil red, efteem'd and honour'd 3 and will be fo much the more, 
by fuch as have by experience found the difficulty, of making 
any one Obfervation certain in that way* 

But that he or any other, that hath a mind to make further 
Tryals and.Obfervations, may be freed from this in oilerable 
troubleand difficulty, I have thought of this following Jnffru- 
menr, by means whereof the Quadrant being oiice ad ju fled, 
and let to the Objects, will continue to befo, for as long a 
time as fhall bedefired, without at all requiring the help of 
any one hand of the Obfervator, though he be but one. 

My 



(#3 

My way then in fiiort is this : I make an Axis of very drf 
■ and flrong Dram-Fir, of a bignefs thick enough for its length, 
to defend it from bending ; at the lower end of this, I fix into 
. the middle of it, ( well bound and hcop'd about with Iron J a 
Center or Point of Steel, very well turn'd, hardned and fharp, 
which is to move in a conical hole fit to receive it, ■ of as good 
and well hardned S r eel ; at the, other end of this Rod,! fix ano- 
ther piece of Steel into the middle thereof, that, immediately 
contiguous to the Wood, hath a Neck very well turn'd and 
hardned, a little tapering from the Wood outward, which is 
to be .moved in a Collar fit for it,as I fliall (hew by and by 5 and 
at a convenient Diftance from ihe laid Neck, as at foinewhat ; 
more then half the Radius of the Inftrirment, is made a Cylin- 
drical Neck, fitted with a Collar of Brafs, withajoyn*, and 
other Apparatus, large enough to carry the Table and InP fo- 
ment firm and true, without Aiding or yielding in its docket, 
after it be once fet. This Axis by the Collar and con cal bole 
below, I place parallel to the Axis, which by fometryals isea- 
fily enough adjufted $ about the Cylindrical Neck, ; at the up- 
per end of this Axis, is a Socket of Brafs faffed with a Sere t v, 
which Socket clafpeth in a Joynt, a Abort Arm, which haihap, 
one end a Ball that is fitted into a Socket, that is fixed under 
the Table and Frame of the Quadrant, and at the o;her end a 
Counterpoife of Lead, to ballance the weight of the whole Ap- 
paratus, about the Quadrant, upon the middle Line of the 
long Axis, then the Table and Quadrant is re&iff d, To as to 
lye in the Plain of the two celeftial Gbje&s, whether Planets 
or fixe Stars, and by the fmall Screws in the Sockets it isfixtin 
that Plain. What further adjuftingis requifuej is done; by 
the help of fmall Screws in the -Quadrant it felf, which are eaii- 
ly enough conceiv'd without Defcription. , The Table being 
adjufted to the Plain of theObjeds, with the Quadrant on it, 
and all counterpoised pretty near by -the poifes underneath 
the Table, and the fixed Sight direded to one of thefaidOb- 
je&s, the faid Table and In ft rument continues to be in that 
Plain, fo long as is defired, without any farther trouble to the 
Obferver, though the Obje&s continually change their places, 
and the fix* Sight remains dire&ed atone of the Qbjefi:*, till 
the other can be found by the moveable Sight;. To effect which 

I % motion 



(68) 

motion ofthe Tableand Mrument, a Wafch-woik is fitted to 
the Axis, foas to make it move iou \A in the fame tin e, with- a 
diurnal revolution ofthe Earth, and confcqucmly to keep even 
pace with the feeming motion of the fixt Stars j the manner of 
doing which is thus : About fame part of the Axis, where us 
moit convenient for the Room in which 'tis to be ufed 3 fix an 
Octant of a Wheel of 3 foot Radius,!et the Rim of this be turn'd 
true to the Centers of the Axis, and cut the edge thereof into 
360 Teeth, there being fo many half minutes of an hour in the 
8th. part cf a whole Revolution, though thefe minutes and 
hours which refpeft the fixt Stars, will be confiderably ffiort- 
er then the folar hours ; then fit a Worm or Screw to thefe 
Teeth, that one revolution of the Worm being made in i, a mi- 
nute may move one Tooth forward ; the revolution of the 
Worm is adjufted by a circular Pendulum, which is carried 
round by a Fiie, moved in the form of a one wheei'd Jack, 
from a fwafh toothed Wheel, faftned upon the fliankof the 
W T orm or Screw above-mention'd ; the weight that carries 
round this Wheel muft hang upon the (bank of the Worm, and 
muft be of afeouca 3d. or 4th. part of the weight of the Qua- 
drant and Table, that it may carry it round fteadily and ftrong- 
ly; and the circular Pendulum muft be foorder'd, thattheOb- 
fervator may at any time of his Obfervation either fborten or 
produce the length thereof, foas to make it move quicker or 
flower, as there fliall be occafion, which is done, by Hiding 
the hole upon which the Pendulum makes its conical motion a 
little higher or lower, without lifting up or letting down the 
Pendulum, orelfeby winding up the Thread of the Pendulum a 
kittle fliorter, or letting it down a little longer, by thehelpof 
a Cylinder, above the hole or apex of the Cone, in which the 
Pendulum is moved. 

This whole Contrivance will be fomewhat better under* 
flood by a Delineation. Let a b then in the 1 5th. Figure re- 
prefent the Axis of Fir or Iron, c the conical Point at the bot- 
tom, d the conical center or hole in which it is to move, e the 
Collar above, in which the tapering Neck of the iron Far f is 
to be moved. The Axis of this is to be placed as exactly as 
may be, parallel to the Axis of the Earth : at the end or head 
of the Iron fg 3 is fitted a Socket hh, withaScrew4, which 

will 



(69 ) 
will fix itto the head in any p [tire. ThisSocket h h in the 
15 and ib Figures, hatha a.r j -ynt to be fhffned by aScrew 
5, in which Joynt is moved a ilrong Bar of Iron, about 4 foot 
' in length, to wit, 2 foot on each fide of the Joynt, the one end 
6 hath a large weight or coumerpoifeof Lead 8, which ferveth 
to counter- ballance the whole weight of the Frame and Inftru- 
ment upon the other, andean be fcrew'd either nearer to or 
farther from the Joynt, as there (hall be occafion for poifing ; 
at the other end of the* Iron is a large Ball of Iron 7, to which 
is fitted alfo a Socket of Brafs 9, with a Screw to fix it and 
move ic, as there fhall be occafion. This Socket is faftned un- 
der the middle of a Table s s, upon the plain fide of which 
the Quadrant is to lye. Upon fome convenient part of this 
Axis is fixed an O&ant or Sextant of a Circle, reprefented in 
the rgth. Figure edge- ways, and intheiyrh. Figurebroad- 
: ways, by 3 3 i i i, whofe circular edge 3 3 is cut into Teeth, as 
! before is directed ; unto thefe is adjufted a Worm or Screw k, 
j which is the Axis or Arbor of the Wheel 111; this Wheel is 
\ moved round by the weight x, whofe Line is coiled round the 
\ Barrel u u, and with it it turneth round the Fiie n n, by the 
I help of a Screw m, fixed upon the Arbor 00, in the manner 
of the Flie of a one wheeled Jack ; this Flie moveth circularly 
the Pendulum pp, in the 15th. and 29th. Figures, which is 
fliortned or lengthned, by flipping up and down the Cylin- 
der qq, the Thread ofthe Pendulum being faftned at r. 

I fhall not now fpend any more time in the Explication of 
the making or contriving the circular Pendulum, referving it 
for another opportunity and Difcourfe, wherein I fhall fhew 
feveral ufeful Contrivances and Inventions about the fame, and 
particularly about this and fome other Experiments of motion, 
which was the caufe of the Invention thereof by me longfince, 
in the year 65. Upon which occafion, I cannot but take no- 
tice of a Publication, made by Chrtfi'tanm Uugenim Zulkhe- 
j mint Conft* F* in his Book call'd, JJorologium Ofciftatorwm five 
demotu Fen&ulorum ad Horologia apt at demonflrationes Geome 
tricae ; containing a fhort Description of a circular Pendulum- - , 
withfomewhat about the Explication of it, without naming, 
me at all, as concem'd therein, though I invented it, and 
brought it into ufe in the year 1665, and in the year 1666, I 

com- 



t7°) 

-.communicated it to the Royal Society, at their publick Meet- 
i ngs, both as to the Theory and Pra&ick thereof, and did more 
particularly explain the Ifocrone motion of the Ball of a Pen- ' 
dulum, in a parabolical Superficies, and the Geometrical and 
Mechanical way of making the fame move in fuch a Superficies, 
by the help of a Paraboloeid, which I caufed alfo to be made 
and lhew'd -before the fame Society, upon feveral days of their 
publick Meeting, where befides many of the Society, were 
divers grangers of forreign parts, This many of the Royal So- 
ciety can bear me witnefs, and the publick Regifters thereof 
do t eft i fie and make appear, and I was told by Sr. Robert Ma- 
ray, that he did then write to Monfeur Zulichem concerning 
the fame* But of this more hereafter, wheal examine fome 
other things in that Book, about finding the defcent of heavy 
Bodies, and of finding the Longitude of places, andpublifh 
fome more certain and practicable ways of doing them. 

This puts me in mind of publishing an Invention, which I 
made and produced before the Royal Society, in the fame 
year 1666, much about the fame time that 1 produced the 
Theory and Experiment of the circular Pendulum compleat, 
which I call'd the perfection of Wheel- work, as being indeed 
founded on a principle capable of the greateft perfection can 
be imagined. It is in ftiorc, Firit, To make a piece of Wheel- 
work fo, that both the Wheel and Pinnion, though of never fo 
fmall afize, ihall have as great a number of Teeth as fhall be 
defired, and yet neither weaken the Work, nor make the Teeth 
fo fmall, as not to be practicable by any ordinary Workman. 
Next, That the motion fhall be fo equally communicated from 
the Wheel to the Pinnion, that the Work being well made, 
there can be no inequality of force or motion communicated. 
Thirdly, That the Point of touching and bearing, ihall beal- 
ways in the Line that joyns the 2 Centers together. Fourthly, 
That it fhall have no manner of rubbing, nor be more difficult 
to be made then the common way of Wheel-work, fave only 
that Workmen have not been accu/tomed to make ir. 

Firft then, If there be a certain number, and no more of 
Teeth required to be made in a fmall Wheel, then mud the 
Wheel and Pinnion confifi of feveral Plates or Wheels, lying 
©r^e befides the other, in the manner they appear in the 20th. 

Figure, 



( 7* ) 

Figure. Where fuppofe it be required, that the Wheel (lull 
| have i ooo Teeth, and the Pinnion ioo, and yet that the Teeth 
both of the Wheel and Pinnion have fufficient flrtngth ; talsp 
10 Plates all of equal bignefsand rhicknefs, and by 2 or more 
[Screws fix them firmly together, as if one Wheel, cut this 
Wheel into too Teeth, and compleat it, then fit the middle 
hole upon the round neck of an Arbor, thenunferew theP.'a^s, 
and place them, in fuch order, that the Teeth may gradually 
follow each other, much after the manner as is expre^ in the 
2©th.- Figure, ( though it be there very ill expr^ff, by reafon 
of the miftake and failure of the Graver ) and ynth fuch fteps, 
that the Jaft Tooth of one Degree, may withitf one ftep anfwer 
to the firft Tooth of the next Degree. I call the to Teeth 
comprehended within the lighter part, abed, or efgh, or 
i klm, a Degree of Teeth in fteps, afid defe, or hgki, 
are Degrees of Notches between thejeeth, and the Tooth be, 
which is the laft towards the righthand, ihould have been pla- 
ced within one ftep as low jtr e h, the firft of the next Degree 
on theleftfide^Xxhotigriitbe much otherwife here graven) 
whence all the inequality in the touching, bearing or rubbing, 
in a Wheel-work thus well made, would be no more then what 
could be between the 2 next Teeth in one of the Degrees,which 
would be much lefs then a 1 oth. part, of what imift ncceflarily 
happen in a Wheel of one Plate of 100 Teeth only. 

Secondlyjf it bedefired,that the Wheel and Pirnion fhould r 
have infinite Teeth, alltheendsof the Teeth in the Degrees of 
the 2 oth. Figure, muft by a Diagonal flope be filed off, and re- 
duced to a frraight, as in the 2r, which may indeed be befl: 
made by one Plate of a convenient thicknefs, which thickntfr 
muft be more or lefs according to the bignefs of the Hoped- 
Tooth. And this is to be always obferved in the cutting there- 
of, (though it be otherwife and very falfly expreft in the 21 
Figure) that the end of one flope Tooth on the one fide, befull 
as forward as the beginning of the next Tooth on the other; 
that is, thattheend b c of one Tooth on the right fide, be full 
as low as e h, the beginning of the next Tooth 00 the lefefide, 
( though by the Gravers miftake it be here quite otherwife 
expreft.) I fhall not fpend more time in explicating the Pinni- 
ons, rstu, rstu, ofthe2oand2i Figures, which are to am 

fwer ■ 



<70 

Aver the Teeth of the Wheels, they beingplain enough to any 
perfona little verfed in Mechanicks, and becaufe the further 
jnd more full Explication of the form and reafon of this and 
other Wheel- work, is comprifed in another Difcourfe, which 

1 may afterwards publiih. 

But to proceed where I left at this Digreffton, to the finiih- 
ing of the Defcription of the Inftrument for moving the Qua- 
drant, fo as alway to refped the Object. The conical hole/ 
in which the end of the Axis is to move, may be made after the 
form exprefTed in the 1 8th. Figure, where a a a a reprefenrs 
an iron Frame fcrew'd faft to the Floor ,b b b b the iron piece, 
containing the conical fteel hole, cccc 4 long Screws, by 
which the piece is moved and fixed in any part of the fpace, in- 
cluded within the Frame a a a a , this by a ftrong fprmging 
Frame underneath, is kept down clofe to the Superficies of the 
Floor, and cannot in any wife totter or fhake. There is no 
great difficulty in the Contrivance, and therefore I fliall pro- 
ceed. 

In the next place then, having fhew'd the way how to keep 
the Inftrument, in the Plain of two Objects that are to be ob- 
ferv'd, Ifljall (hew, by what means a Quadrant may be kept 
always Perpendicular, and in the Azimuth of the celeftial Ob- 
ject. And this I do, by a fmall addition to the former Con- 
trivance ; that is, Let ab in the 22 Figure, reprefent the 
Axis defcribed in the former Contrivance, accommodated 
with all the Contrivances- of the moveable Center below, of 
the Cock- work of the circular Pendulum, to keep it moving 
equally round in the middle, and of the Collar e above. But 
unto the fmall Neck f muftbejoyn'da femi-circnlar piece of 3 
Iron c d, with a Center-hole in each arm at c and d, to re- 
ceive the Pevots i i, of the circular piece of Iron x, in the 

2 2 and 23 Figures, upon the fecond Floor 00, muftbefted- 
faftly fixed a Bow or Frame of Iron h h, which mil ft have a 
hole through it, exactly over the middle of the Plate x, this is 
to be a Collar for the Neck k, of a perpendicular Axis 1 k, 
which by means of a moveable Center fr&ed in the deling-, in 
which the Point 1 moves, may be exactly adju (red to a Per- 
pendicularity ; to this Axis at right Angles is fixed a Frame 
m m, fteadied by the Brakets or Braces n n j upon this Frame 

the 



( 73) 

the fixed Sights oFthe Quadrant, are laid and adjufted to an 
exact Horizon tali ty, and the Plain of the Quadrant being once 
adjufted to the Plain of the celeftial Object, will by the circu- 
| lar Pendulum moving the Axis a b, in an equal motion with 
that of the Object about the Axis of the Earth, be always 
kept in the Plain of the Object, whofe Azimuth and Altitude is 
to be obferved. Now the motion of the under or inclining 
Axis a b, is communicated to the perpendicular Axis 1 k, 
by means of the circular Plate x, in the 22 and 23 Figures, 
for the femi-circular Arms c d of the lower Axis, taking hold 
of the Points 11 of the Plate x, and the femi-circular Arms of 
the upper Axis, taking hold of the Points 22 of the faid Plate, 
the perpendicular Axis is moved in a proportionate motion 
with the inclining Axis a b, which Proportion is Geometri- 
cally and ftrictly iuch as it ought to be, to keep the Plain of 
the Quadrant exactly in the Azimuth of the celeftial Object, as 
any one never fo little verfed in Geometry, will eafily find ; 
and I fhall hereafter more at large demonftrate, when I come to 
ihew, what ufe I have made of this Joynt, for a univerfaLIn- 
ftrument for Dialling, for equalling of time, for making the 
Hand of a Clock move in the Shadow of a Style, and for per- 
forming a multitude of other Mechanical Operations. 

The next thing I have to explain, is the way of finding how 
many Revolutions of the Screw, and what parts of a Revoluti- 
on go to make a right Angle, or 90 Degrees upon theQuadrant. 
For the doing of which, I muft, in a place where I can have a 
good Profpedt for a femi-Circle, firft direct both the Sights of 
the Telefcopes di redly at the fame Object, and the fame Point 
thereof, and then redtifie the Indices to o, or the beginning of 
the Divifions ; then I turn the Screw, till as near as I can mea- 
fure with Compaffes, the moveable Telefcope hath moved a 
Quadrant, and through the three Telefcopes take notice of 
three Points in the Horizon, that is to fay, two Points exactly 
oppofite one to another, in re{pect of the Center of the Qua- 
drant, and a third pretty near the middle between them, in 
the fame refpect, which I further adjuft thus ; I fhew'd before 
how I rectified the fixed Sights, fb as to look exactly forwards 
and backwards, which being accordingly done, I obferve the 
fuppofed right Angle, with the moveable Sight on theQuadrant, 

K and 



(74) 

and with the Sight fixt on the Quadrant looking forwards, and 
note diligently the twoObje&s pointed at, then without moving 
the Screw, or moveable Arm upon the Quadrant, I find thofeOb- 
jeds throughthe moveableSight,and the fixt Sight,looking back- 
wards, and directing one of the Sights exactly to one Point, I ob- 
ferve how much the other doth vary from the other Object, either 
by being within it or without it ; then I half that Difference, as 
near as I canjudge by my Sight, and move the moveable Sightby 
the help of the Screw, fo as to refpect the middle Point: Then 
I obferve this fecond found Angle, by the flxt Sight looking 
forwards, and by the moveable Sight, and fee whether there be 
any Difference, and if I find any, as near as poflible, I adjuft it 
again, to half this laft difference, and fo continue to examine 
and adjuft, till I am certain, that the Angles on each fide of the 
moveable Tube, between the fame and the Sights, looking for- 
wards and backwards, are equal to each other, and confe- 
quently are both right Angles, or Quadrants of a Circle. 
Which when I have found, I obferve, by the Indices on the 
Screw-Plate and Limb, how many Revolutions, and what part 
of a Revolution, the Screw hath been turned to open that An- 
gle; this Number I fet, as the Number anfwering to 90 De- 
grees, and dividing that Number into 90 equal parts, I have 
the Numbers that belong to every Degree, and dividing the 
common Difference between them into 60 parts, I find the 
Numbers anfwering to the Minutes of the Quadrant, and di- 
viding the common Difference between the Minutes into 60 
parts, I eafily make the Numbers anfwering to the Seconds; 
but thefe will be needlefs, for fubdudting the next Number, 
lefs then it in the Table from the Number obferved, you 
have the Degree and Minute, and fome Number perhaps over, 
which may prefently be found by one fmall Table of the com- 
mon Differences of Seconds. See page $$. 

Here methinks I hear fome object poffibly, That the Divifi- 
ons on the Quadrant, do not exactly correspond to the Divi- 
iions made on the Plate. I anfwer, That in part they do, and 
in part they do not. Firft, They concur, in that all the Di- 
vifions made by whole Revolutions, (hew exa&ly the fame by 
the Indices, that they do upon the Quadrant. Secondly, I 
fay, in part they do not, that is, the parts of any fingle Revo- 
lution, 



(75) 

lution, are not exactly and Mathematically the fame pointed 
out by the Index, upon a Ring equally divided, that are made 
upon the Limb of the Quadrant. But yet, I fay, they are 
fenfibly equal even to the fenfe, affifted by a 60 foot Telef- 
cope, and confequently need no manner of rectification ; but 
yet if any one will be fo curious and nice, he may make the 
Divifions on the Index-Ring, according to the proportion of 
the Differences of the Tangents, that are fubtended within 
half the compafs of the diftance of the two next Threads. As 
fuppofe in the above-meution'd iuftance, half the Diftance of 
two Threads be the Tangent of three Minutes, or thereabout ; 
if we examine any large Table of Natural Tangents, we mail 
find the Differences between the Minutes themfelves, even till 
fix Minutes, (which is much more then double three) doth 
not differ above one or two parts of a thoufand thoufand, 
which is 1000 times more nice, then our Sight, even with 
Glaffes, can arrive to, much lefs then will be the difference 
between the Differences of the Seconds; and therefore it will 
be a nicenefs meerly notional, and of no ufe, and as fuch, 
ought to be omitted, and the plain and equal Divifions made 
ufe of, they being as to all fenfe true and perfeft, and proper 
Divifions, though as to curiofity of Theory and Calculation, 
unequal. 

Now I have done, poffibly fome may fay, To what pur- 
pofe all this curiofity ? To which I anfwer, That though pof- 
fibly in many common cafes 'tis of but little value, yet I con- 
ceive in general, that it is of infinite value, to any that mail de- 
{ign to improve Geography, Aftronomy, Navigation, Philofo- 
phy, Phyficks, &c!"- And to inftance in fome particulars, I 
conceive, 

Firft, That one ufe of this Inftrument, may be for taking 
the exa& Refraction of the Air, from the Horizon to the Ze- 
nith; by which we mall be able not only to rectifie all Ob- 
fervations, and clear them from Refractions, which in fome 
Obfervations, efpecially thofe of Parallax, is abfolutely ne- 
ceflary, but it may give us a new means to judge of the quali- 
ties and conftitutions of the Air, as to the feafons of the year, 
and the temperature of the weather, which are to fucceed, 
For 'tis moft certain, that there is as great a variety in the re- 

K z fractive- 



(76) 
fractivenefs of the Air, as there is in the heat and cold, gravity 
and levity, drynefs and moifture, rarefaction and condeniati- 
on thereof, and fometimes when none of thofe do feem at all to 
be fenfibly alter'd, its refract ivenefs hath been very much va- 
ried, which change does feem to proceed from fome alterati- 
ons in the upper Regions thereof, far removed from the Super- 
ficies of the Earth, and is fometimes many days in defcendino- 
and fermenting, as it were deeper and deeper, into the lower 
Regions of the Air, before it defcend fo low as the bottom 
thereof next the Earth. But of this much more in another 
place. 

A fecond ufe is for regulating the places of the fixt Stars, as 
to their Longitudes and Latitudes, and Diftances from one ano- 
ther, efpecially thofe within the Zodiack, by which we mall 
in a fliort time be able to judge, whether thofe Bodies that we 
account fo fixt and conftant, do not vary their Pofitions one 
to another, which I have very good grounds to believe they 
do. 

A third ufe of this Inftrument, is for regulating the places 
of the Planets, by their Appulfes to thofe fixt Stars, fo that 
not only Aftronomy will be perfected, but the Longitude of 
places upon the Earth, (a thing fo highly advantageous for 
Trade and Navigation) will of confequence follow, which 
without fuch an Inftrument as this, is in vain expected from 
the Heavens. 

A fourth ufe of this may be for ftating the exact: Latitude of 
places to a Second, whereby we mail quickly know, whe- 
ther thofe Latitudes do vary, as well as the variation of the 
Loadftone, which hath been conjectur'd, not without fome- 
what of probability, but is hardly to be determined, without 
fome fuch accurate wayof Tryal, as this Inftrument is capable 
of performing, 

A fifth ufe of it may be, for examining what influence the 
approach or recefs of the other Planets have upon the Earth, 
as to its Periodical motion, and what influence the Earth hath 
upon them as to theirs ; for I have good ground to believe, 
each of thefe to have influence upon one another, and to caufe 
fuch motions, as have hitherto much confounded all Aftrono- 
mical Hypothefes and Calculations : Of which I (hall fay more 

A 



(77) 

A fixth life may be for meafuring the quantity of a Degree 
Itpon the Earth ; the beft Experiment of that kind, that is yet 
feublick to the World, is that of Mr. Norwood, made between 
f^ondon and2V£: But if we examine with what Inftruments he 
triade it, we (hall rind, that he was not certain in either of his 
■Latitudes to a Minute, and confequently could not be certain 
bf the quantity of the Earth, anfwering to his fuppofed mark 
to two miles, and confequently it could not be made the com- 
tnon ftandard of all meafure. But by the means of this Qua- 
idrant, all Latitudes may be certainly taken to a Second, and 
[confequently the error in 150 miles, cannot be more then the 
Loth, part of a mib, and confequently a foot, or yard, or rod, 
■this way ftated, cannot vary above a 6000 part of its length, 

which is fufficiently accurate for a univerfal and common 
Jftandard of all meafure and quantity, to which all other mea- 
sures in the World fhould be refer r'd and proportioned. 
IThis was the occaiion of the contriving and making thereof; 
|His Sacred Majefty having commanded me to fee that Exper- 
iment accurately performed, and to give Him a true Account 

thereof, which had been before this performed, had not my 
jindifpofition of health prevented. 

A feventh ufe may be for meafuring the Diftance between 
{two places, exactly in a ftraight Line. This it will perform 

to admiration, by the exactnefs of taking the Angles, if fome 
ilength be exactly meafured at the place that is to be the Ob- 
feed, infomuch that 'tis hardly poffible, by any other means in 

the World, to come to that exactnefs, nay, though there were 
ja continued Plain extended between the two places, whole 
iDiifances are to be found, and the fame were carefully meafu- 
. red with Chains, Rods, or Wheels. By this means the Di- 
(iftance of a Ship on the Sea, can be found more exactly, then 
jany other way whatfoever, by one or two Stations, and a 
fmultitude of Philofophical Tryals under this Head, which are 
(jnot practicably to be done with any tolerable accuratenefs, 
|by other ways. 

An eight ufe may be for taking the exact Diameters of the Sun, 
llMoon, and Planets, even to a Second, and the Diftance of the 
ijfmaller appearing Planets from the. fixt Stars, near adjoyning. 
J Now becaufe for this Defign, it may perhaps feem a little too 

cum- 



( /B ) 

cumberfom, and by reafon of its fhort Tubes, fomewhat too 
imall, I have therefore contrived an Inftrument of 6 times the 
length or radius, which will take in an Angle of about 5 De- 
grees, and yet take in the whole Angle by one glance of the 
eye, and determine the meafure thereof to lefs than a Second. 
I have likewife invented and made a new Heliofcope, by 
which the Body of the Sun may be look'd on as inoffenfive'ly to 
the eye, as a (beet of white Paper; of great ufe for fuch, as 
will make Phyfical Obfervations of that glorious Body. Thefe 
I will in fome enfuing Papers defcribe. 

A ninth may be for exa&ly taking the Level, for the con- 
veyance of a River or Water' from place to place ; and under 
that Head of performing infinite of Philofophical Experiments, 
which can hardly be try'd by any other way in the World^ 
about the Refraaivenefs of the Air near the Earth, whereby 
diftant places fometimes appear, and fometimes difappear, 
under the Horizon. By this means alio the Rotundity of the 
Earth may be truely found, vaftly furpaffing any thing per- 
formed by the beft Levels yet known. To this we may add, 
the height of Hils, if their diftance be known, or their di- 
flance, if their height be known. 

I could have enlarged upon thefe, and have named divers 
others; but defigning it only as an Anfwer to fuch, as may 
captioufly put fuch a Queftion, I mail rather leave the plea- 
fure of rinding them, to fuch as (hall really feek them, to be at 
fifted thereby in their own undertakings. 

FINIS. 



Errata. 
pAg.2.1.i3.r./op.6.1.i4.^ 

r.%.32.p.i3.1.28.r.^.3i.p..i8.1.39.r.>^^^.p.2i.U6. 
r. denaminuta,p. 21 .1.2 7. r.difcriminatim. p. 22.1.3^.^.35. P* 28.1.-2 4 . 
r.^^.p.32l.2i.r.y^^ 
t.admoveant. p.4o.l.39.deley£« 



A 

DESCRIPTION 

OF 




And forae other 

INSTRUMENTS 

M AD E B Y 

R Olll T H O K E, 
Fellow of the Royal Society. 

Hos ego, &c. 
Sic vos turn vobis- ' 



L O N D O N, 

ntcd by T. K. for John sJWartyn Printer to the Bjoyd Society^ 
v at the Bel/'mSu FmIs Church-yard, 1676. 



C i ) 



N»mb. 3< 




A 




O F 



HELIOSCOPES 



And fome other 








>w« 



H E necefiary avocations of bufinefs, and the 
urgent importunity of fqme, forthefpeedy 
publication of my Animadverfions , made 
me conclude them in the Eleventh fheet , 
without flaying to Explicate feveral things 
which I defigned to go along with tbem. 
But having now retrieved a little more of 
leafure, both for DeUneatim and Defer if tkn\ for a further 
elucidation of what I have faid, J fhail make it my third 
Attempt, to explain ; 

Firft, J. Heliofcope tohokfifon the body of the Sm, without 
my offence tothe Obfervers eye. 

B Secondly 5 




CO 

Secondly, A way offlmtning reflexive and refractive Tele- 
fcopes. 

Thirdly , A way for ujing a x Glafs of any length, without mo- 
ving the Tube* 

Fourthly, An In fir ument fir taking the Diameters of the 
Sun, Moon and Planets, or for taking any other Difiances, to 
five or ten Degree^ to the certainty of a Second. Two of theft 
I prormfed in the j%th. or laft page of my Animadverficns, 
and the other fall in as analogous to them. 

Fifthly, An Infirument fir describing all manner of 'Dials, by 
the tangent projection. 

j i . For adjufiing the Band of a clock, (b as to make it 

move in thefhadow of a Di*\,wkofe ftyle is parallel to 

the Axis :_ Or, 

I 2. In the Azimuth of any Celefiial Body, that is, in the 

Jhadow of an upright y or any other way inclining 

Sixthly, Sty/ey upon any plain. 

Tkeufes<3. For makinga Iland move according to the true W- 
thereof \ \ quation of Timg. 



J 4. For making all manner of Elliptical Dials , in 
I Mr. Fofter'j way, &c; 
,5. For. communicating a circular motion in a Curve 
>•[ \ Lwe^witMoui anyfhaking: And for divers other 

<- exeellencpUFpofds. • ■• 

Alid"fi r ft ; For a HELIO SpOPE which /ball Jo take 
t>ff the brightness of the Sun , as that the weakefl eye may look 
upon it, at anytime^ without theleaft offences' My^co^rfrance 
is , By often reflating the R'ayes from the furfaces of black 
Glaffes, whipfa are-grownd very exaftly , flat , and very 
W.eli polifhed /fo to diminifli the Radiations, that at length 
they become is weak and faint as thofe of the Moon in the 
twilight, fo that one may with eafe, and very much plea fu re, 
view, examine and defcribe the phafe of the Sun , and the 
macuUmdfacul£ thereof, if any fuch happen to appear when 
tte Obfervation is made, and it gives a good opportunity of 
difcovering them, before we have any ad vertifement thereof 
from others. The reafon of which will be fufficiently plain 
i-©,£licb asconilder, how great a Entity of the ray s*rjf ; Light 

is 



(3 ) 

is loft by every refle&ion, and that every reflection doth 
duplicate, triplicate, quadruplicate, quintuplicatc , &c. 
the firft proporrion of lofs. For Inflance : 

Suppofe I have a Heliofiofe made of an Object Glafs , 
an Eye Glafs, and four Reflecting Glaffes, and that, by the firft 
reflection, I lofe \ of the Direct light ," I affirm there will re- 
main but ^ part of the Direct rays of the Sun, which can fall 
upon the eye at the laft , for if every reflection doth lofe 
I of its Rays, and reflecl: but ^ and that quarter Jofeth |, and 
reflects only ~ of its received Light, there will- remain but 
£ pan of The whole, and if this fixteenth part lofeth three 
quarters of its Rays, and reflects only a fourth, it will follow, 
the remainder will only be g part of the whole , and if that be 
once more reflected, the Ray will return but with ^part of its 
firft light. 

This, although it be obvious , and eafie enough now it is 
known,yet I do not find that any Perfon hath yet had thoughts 
of applying it to this ufe. The generality of Obfervers have 
hitherto made ufe of, either fome very opacous and thick 
GJafles next the Eye 3 whether of red , green, blew, or purple 
Glafs; others have diminished the Radiation, by covering 
the Glaffes with a very thick and clofe coat of the foot of a 
Lamp; others, by cafting the figure upon a piece of white 
Paper, whence 'tis reflected to the eye ; Others have contra- 
cted the Aperture into a lefs circle, and thereby let in lefs 
Light, and fo make ufe of one Angle Ray inftead of a pencil 
of Rayes ; Others have expanded the figure of the Sun , by 
the help of Eye Glaffes, into a circle of ten , twenty, or an 
hundred times its Diameter. But none of ail thefe waies 
do come near this which I now defcribe by the help of three, 
four,or more Refledions,as any one upon trial will very plain- 
ly difcover. 

Firft, As to the coloured Glaffes, I cannot at all approve 
of them , becaufe they, tinge the Raves into the fame colour, 
andconfequently takeoff the truth of the appearance, as to 
Colour; befides, it fuperinduces a hazinefs and dimnefs 
upon the Figure, fo that it doth not appear fharp and di- 
ftinft. The fame inconvenience is alfo produced by Monfieur 
Bugenius's way , of covering the Glafs with the foot of a 

B 2 Lamp, 



(4 ) 
Lamp,though not to fo great a degree. The Figure on paper, 
or a fmooth white furface is not magnified enough, nor the 
difference of fiiadows fo very diftincr, though thatdoth very 
well, if the furface be very finooth, and the Objeft be magni- 
fied by a Hand Glafs. That by the con traced Aperture is the 
worft of all, by reafan of a certain propriety of Light not 
taken notice of yet by Optick Writers, the edges of Ob- 
jects feeming ragged, of which I have hinted fomewhat inmy 
Animadverfions, pag.3 5 , and fhall fhortly fay much more, the 
whole ground of Of ticks depending thereon. 

The way of expanding the figure of the Sun by the Eye 
Glafs, to mefeems the beft of all the reft , but that is apt to 
vitiate the Figure, to fuper* induce fomewhat of Colour, and 
doth not give the fmalleft diftinftions of lights and fiiadows, 
without fomewhat of colour, and fomewhat of hazinefs arid 
dimnefs. 

The GlalTes of this H E L I O S C .0 P E may be made ei- 
ther by refraiHing or refetting Spherical GlalTes. The beft way 
for raking, in a large Angle, is , the ufing ref rafting GlalTes, 
both for the Objeft and Eye GlalTes; but the beft way for 
taking in a final I part, and for avoiding hazinefs , dimnefs, and 
colours, is 3 by Reflection, either in part, or in whole ; that 
i.s, either to make the Objeft Glafs only by way of Refie- 
ftion, and the Eye Glafs by that of Refrattion , or, both the 
ObjecVglafs and Eye Glafs alio by refleclion, and to have no 
refraction at all. The feveral waies of doing which I have 
reprefented in the adjoyning Table, wherein I have expreiTed 
renfeveral waies of placing the feveral Glades, fo as. to be fit 
for the ufe defigned. 

The firft way reprefented in the firft Figure, is, a fixty foot 
Objeft-Glafs, contracted into a twelve foot Tube, by the help 
of four feveral Reflecting- plates placed between the Objeft- 
Glafs and Eye-Glafs. The Experiment of doing which, I 
produced and fhewed before the Royal Society , at divers of 
their publick Meetings n^rundelhoufe, in the year 1668, 
and it remains upon their Regifter. 

This (as I then fheived) would be of exceeding great ufe 
in all manner of Rerftettives and Telefeopes , if we could find 
a good material that would make the Reflections very ftrong 

and 



and full. And that would not be fubjeft to lo/e its Figure, 
which all our fpecular Mertals are very apt to do 5 for, by ir, 
'twould be poffible to contract [he Tubes for long Glades 
into very fliort lengths , and fo make them of eafie lire and ma- 
nage. 

This I attempted with feveral forts of Mettal , made with 
#, $, £, Antimony and Jrfenick, but mod of thefe compound 
Mettals I found to be very fpongy , and confequently in the 
laftpolifh to receive, though a very glaring polifh , yet fuch 
as did much confound the Objeft by a kind of hazinefs , efpe- 
cialiy if Putty be ufed to glafe it, and, for this purpofe, Putty 
unifl not in any wife , that I yet know of, be ufed, it being 
fo very apt to round ofF the edges of pores or fcratches, which 
does much contribute to the hazinefs and confufion of the Ob- 
ject _"■ 

If I made'ufeof GlafTes foil'd with Quickfther , which I 
found to give much the beft. reflection, yet 1 found (his incon- 
venience, that a considerable part of the Ray was loft, by the 
double reflection at theunfoird fuperficies of the Glafs. The 
fi*ft from the furface of the Glafs before it entred, this, as it 
weakned the Ray, fo mingling with the other reflection that 
came from the bottom , it created force kind of hazinefs and 
confufion, if the two fuperficies of the Glafs were parallel, 
but if they were not parallel, it fuperinduced_fomewhat of- 
Colour, uniefs it were helped by a contrary refraftion in a 
fecond ReflecYmg- glafs, after rhe manner of that which is de- 
lineated in the fifth Figure, where let a b reprefent the Objett- 
Glafs, eg thefirft Refleding-plate,whofe thinneft fide is iqc r 
and d 6 the fecond Refleding-plate, whofe thinneft part 
is towards 9, which doth thereby take off the firft Refraction 
of*£, anddeflroy the Colours fuperinduced by the firfr. 
The Ray alfo was weakned much more from the fecond 
reflection it fuffercd at the unfoil'd fuperficies of the Glafs, 
from the refle&ion of the Air, or <ether,wh\ch is much (Ironger 
than that of Glafs, at its re-entring into the Air. Befides this, 
I find that the fubftance of mod: Glafs is fo imperfeftly mixr, 
that there is in the very befl much of veinynefs and inequa- 
lity of Refra&ion in the parts thereof, and thence, though 

there 



( 6) 

there were no vifible vein appearing in the body of the Glafs, 
and though both the furfaces thereof were very truly figured 
and polifhed, yet there was fome kind of dimnefs fuperindu- 
*;ed upon the Obje&s, by the rays paiTing through thofe 
GlafTes. But this was not in all, for I found fome that did 
very well anfwer my expe&ation , and I am very apt to be- 
lieve, that if a pot of Glafs were made on purpofe , by a way 
I know, the body thereof might be made perfetfly clear, 
uniform, and tranfparent, without blebs, veins, or fands^ 
which, when I have leafure and opportunity I defign to ex- 
perience farther But this only by ihe by , in relation to the 
fliortning the Tubes of Telefcopes for the Moon , Flanets, and 
other Qbje&s, becaufeit is not at all to our prefent purpofe of 
making a HeUofcofe, where we make ufe only of the reflection 
of the fir/I fuperficiesof the .Glafs, and where Our main aim 
anddefign, is, the lofs of the ftrength and brightnefs of the 
Rays, and not l for preserving the ftrength and brisknefsof 
the Rays , or augmenting them. And therefore for this ufe, 
the befV material I have yet met with, is, black Glafs, black 
Marble, and Glafs of Antimony. For thefe fubftances being 
very dark and opaque, do refled but a very final! part of 
the Raies that fall upon it, and none of thofethat penetrate 
into it,efpecially if they be thick; and being ofa very hard and 
permanent fu bftance , are capable of receiving a very curious 
and exact polifli,and qualified fufficiently to retain and keep 
ir, without receiving injury from the Air, or ordinary wiping. 
But in the making of thefe Gjaffes for Long Telejcofes , very 
great care and diligence rnuft be ufed to make them of a true, 
fiat, and fo much the more, by how much the nearer they are 
placed to the Objecl-Glafs,and the further from the Eye-Glafs - y 
alktleerrouratagreat di fiance from the eye being va/lly mag- 
nified to the eye at that diftaece , whereas a greater becomes 
infenfible, if it be near the eye. Let a, £, in the firft, reprefenr a 
fixty foot Glafs, w ho fe focus is at 03 let a c d e f , and 
b gh ik o, reprefent the two fide Rayes of the pencil of light, 
this Pencil, by the four Refleding furfaces O »», & % 9 c ,, £ k) 
is broken into five fhorter lengths ( » f anfwering toed, y to 
gb t *• to de t 8/ to hi, «{ to <r/, and ** to i k, and 

laftly, 



(7) 

Jaftly,^ • and xo, to ft and key as will be'fufficientty plain 
to any one that will but confider the Scheme. 

By this way four fifths of the length of the Tube is taken 
away, which is the mo ft that can be taken away by four Re- 
flections , every refle&ion running the whole length of the. 
Tube, a letter part of the length may be taken away in any 
proportion afligned, as in the fecond contrivance, defcribed 
in the fecond Figure , two thirds are taken off, when the fame 
Letters anfwer to the Objed-Glafs, Eye-Glafs, the flexures of 
the fide Rays of the Pencil, and the ReflecYing-plates that make 
thofe flexures. The third and fourteenth Figures reprcfent the 
Tube fihortned by two or three reflections , and fo ferves 
tofhorten the Tube by two thirds only. Thefe are of ufe for 
a very ftrong Eye and with a fmall aperture of the ObjecV 
Glafs,and when the Sun is near the Horizon, or its light is a 
little diminiflied, by a Fogg, thin Clouds, or the like. 

If it be thought more convenient to have this long Tube 
to lie alwaies Horizontal, and confequentiy, that there fhould 
be no need of having a Pole or Engine toraifetheTube: It 
may be framed fomewhat like that in the fourth Figure, where 
the fame Letters anfwer to all the parts above-mentioned, 
or elfe like that in the fixth Figure , the Letters of both 
which being the fame with the former, will eafily explain them. 

Now in all thefe, and 20 other contrivancesof this nature 
with one, two, three, or four Reflecting- plates which may Le 
prefently thought of, the fight is directed exactly at the Sun, 
fothat there will be little difficulty of finding" it ar'er the 
Glaffes are fixt to their due lengths and portions. 
s I explained alfo at the fame time to the Royal Society ; at 
their publick Meeting at Arundel-houfe, feveral other waies of 
facilitating the ufe of very long Glaffes , for other Objects in 
the heaven, by the help of one Reflecting plate only, and that 
was by a Tube .fixed, either perpendicularly, horizontally, 
or obliquely, for it mattered not whether as to the feeing the 
Object in any part of the Heaven , fuppofing other circum- 
ilances hindred not , and the objeft could be as eafily found 
as by the commonTdefcope* of the fame length, But of thefe 
eifewhere* 

Thefe contrivances with four Refleffhns, nuy be made ufe 



(8 ) 

of by fuch whofe fight is weak , but fuch as can endure it 
fomewhat brighter, and would fee the parts more flrong, may 
makeufeof one of three Refk&ions only, like that of Fig. 14. 
which doth bell fuit my eye. 

Next, this Heliofeofe may be made by Refieftion only, with- 
out any Refra&iott, and that may be done either in the man- 
ner of that in the feventh Figure, when a b reprefents a con- 
cave furface of a black Glafs, whofe focus is , which, for In- 
fiance, we will fuppofe at the diftance of forty foot, c d repre- 
fents a clear plate of Glafs of two flat furfaces,whicfrare made 
not parallel but a little inclining, fo as the reflection from that 
fide which is furtheft from the concave may be caft another 
way,and not fall at all upon the third Refleding-plate • ?, and 
becaufe the wedg-like form of this tranfparent plate of Glafs, 
cd, will'caufe a refra&ion , and confequently a coloration of 
the Ray $ therefore there muft be another wedg-like Plate 
exa&ly as may be like the former, which at fome diftance , as 
zimp, where the reflection will not come to. fall upon the 
Plate, if mu'ft be fo fixed that the thinneft part of this may 
lie ju'ft upon the thickeft part of e d, and the thickeft of this 
over the thinneft of that, by which means both the falfe refle- 
ctions and refractions will be removed. From e £ the Rays are 
reflected to y 0, and from y 9 to the focus, and fo through the 
lens, z\ to the eye x. This I take to be the beff by Reflection ; 
but it may be twenty other waies contrived , which f fhall 
not now fpend more time in defchbing, it being fo eafie a mat- 
ter from 1 the confideration of thefe I have mentioned, to make 
an hundred other variations of the principle. 

To this Heliofcope may be fitted Inftruments for meafuring 
the Macula i facttU , and NebuU , vifible in the body of 
the Sun, as alfo the fpaces pafTed by them in a day, two, three, 
ten, &c. together with the variation of their Figures and Mag- 
nitudes $ but the diameter of the body of the Sun will be bet- 
ter taken by the following fnffrument. And by reafon that ft; 
will be often neceffary to draw their figures more exactly, the 
Engine that I have defer ibed in my Ammadverftom, in the 
67, 68,and 6^pages ) \my be madeufeof to keep the Heliofcope 
al waies directed at the body of the Sun, which will be no final! 
eafe to an Obferver, that is to delineate the figures on Paper. 

When 



C 9 ) 
When the brightnefs and radiation of the ^Moonyenm or Jtt* 
piter, do fomewhat offend the eye, they will prefently lofe 
their beards and look very diftinct, if one refle&ion from 
glafs be made ufe,of in the Telefcope. 

Another Inftrurnent 1 promifed to defcribe, is, for taking 
any fuch Diameters tr unfits, ordinance to the certainty of a 
fecond Minute, by which more may be done for the finding 
the Parallax of the fu per ion r Planets, and the Longitude on 
the Earth , then hath been ever yet done by all the Inftru- 
ments that have been ufed in the World* 

i. This is madeexaftly, in all particulars like the Qua- 
drant, as to its hollow centre, Screwd-limb, Screw-frame, 
and long Rod to turn the Screw from the .Centre ; and that 
the Screw-frarae may be kept down the truer, upon the 
edge of the Limb, there fhould be made a fmaMrni to clafp 
behind the inward limb of the Inftrument , after the manner 
reprefented in the %th. Figure by *v, by which means the 
Screw will be kept clofe, fteady, and eaven to the outward 
edge of the Limb* The Letters in this $th. Figure being the 
fame with thofe of the i and nth. Figures of the Jnimadver- 
Jions, and reprefenting the lame parts, need no further expla- 
nation. 

2. Infteadof this Screw upon a circular Limb, a Screw may 
bemadetornoveuponaftraight Limb, or Ruler- theendof 
which muft move upon Centres or Rowlers , the centres or 
axes of which Rowlers muft be exactly in the fame line, 
when both the Perfpeftive-fights are adjufted to the fame Ob- 
Jed, and the divifions began. The fame thing may be done by 
a ftraight Screw , in the manner of a pair of dividing Com- 
pajfes, where the fame care muft alfobe had, that the axes of 
the Rowlers muft be exaftly in the fame line , and the fides of 
the Incompaffing-fcrew , being made of fteel, muft be made to 
fpring about the long Straight-fcrew ; this long Screw muft 
bemadeof fteelof half an inch of diameter at leaft, if itbe 
made 1 8 inches long, and 'twill be beft to fcrevv it with a final! 
thred , otherwife it will be apt to be moved out of * ftraight 
by fcrewing a large thred ; and the thred , whether greater or 
lefs, muft be made by degrees with a pair of cutting- ftocks 3 
that may be fet clofer every time of fcrewing. 

C The 



( io > 

The manner of contriving the Centres and Sockets may be 
feen in the 1 2 and 1 3 Figures, where the 1 3 reprefents it in an 
end- way Profpeft, and the 12 in a lateral or fide-Profped ; 
1 is the Rowler of the upper Tube, and 2 of the under, 33 the 
Screws to faften them in the holes , 44 the incompaffing or 
Socket-fcrew which fpringeth ciofe to the Cylinder^, 6, the 
Cy Under ical finooth Socket which guides the Cylindrical- 
fcrew,fo as to make its Axis pafs exafily over the center of the 
Rowler 22, and which., by means of a Ring 7 on the fcrew, 
keepeth the pointed- end thereof 8 againft theft&y or por». 
tance9; 'tis not difficult how to make a Dividing<plate, and 
an Hand or Index thereunto, nor how it may be turned from 
the centre of the. two Tubes by along Rod, as in the 8th. fi- 
gure $, nor will it be difficult , after it is known by Obferva-r 
tion, bow n$fiy Revolutions, and what part of a Revolution 
anfwers to five whole degrees, to calculate a Table of Sub- 
tenfes^ which (hall ffcewvvhat part thereof goeth to make the 
fuktenje of every Minute and Second of the faid angle. 

3*The fame thing in the year 1 665,1 performed by a Rowler, 
rowling upon the limb of the §Hfidr*nt n by the help of two 
Wires which were coy led about thofe Rowlers , and the ends 
thereof were faftned upon the limb of the Quadrant 5 for, 
by a large index on the end of this Rowler, I was able to move 
the arm of the Inftrument to any fifth Second of the, jg^* 
drM, with great eafe and certainty. 

I alfo at the fame time made another Frame with a ftralght 
Screw, which opened to five degrees only, with Tumbrels or 
Rowlers like a pair of dividing Gompaffes ( after the fame 
manner with this I have newly defcribed , for taking Dia- 
meter 1 or Difiames to five degrees) ardLby the help of very 
curious Lines drawn upon a fmooth Glafs- plate , and Points 
^ery curioufly made at every five degrees on the limbof the 
^u&drant^ or Inftrument on which it was fixt, and the help 
of a very deep PUm convex lens y whofe plain fide was turned 
downwards towards the Plate , and the convex fide towards 
the eye, the faid Frame was moveable from five degrees to 
five degrees, upon the whole limb of the SuadrAnt or Inftru- 
inent, by which/ Inftrument I could with great eafe aflu- 
and accurate divide an angle into every Eve Seconds^ 

and 



( H) 

and confequcntly take any angle to the accuratenefs of five 
Seconds ; for, removing the Frame to the next divifion , lefs 
than the Angle defired, and then by the Glafs,fixing one of the 
Arms that had the place, exa&ly over the hole or point of 
divifion , by the Screw the remaining part of the Angle could 
be exa&ly meafured. 

As to the method of dividing any of thefe, the beft way 
will be to meafure upon forae Plain iooq, 1 500, or 2000 foot 
in lengch, by two Rods of twenty foot long a piece, or elfe 
by Wires drained with weights, the way of which I flhall 
(hortly defcribe : Beginning from the very centre of the In- 
ftrument, and at the end thereof, to fee up fo many Deal- 
boards joy ned to the end of each other in a ftreight line, or 
elfe to (train a pretty big Line, which fhall cut the meafured 
line of difiance from the center of the Inftrument at Right- 
angles, and then by a Table of natural tangents , according to 
the diftance from the centre of the Quadrant, put as Radio*, 
to fet and mark off upon thofe Boards or Lines the divifions 
of Degrees and Minutes, by Compares or Rules, as exactly as 
may be, and mark them accordingly , that the Degrees may be 
diftinguifted very plainly from the Minutes : Then having ad- 
justed the Inftrument, fo as to fee the beginning of thofe Divi- 
fions through both the Tubes at once , to fet both the Indices 
to o t or the beginning of the divifions, then keeping the under- 
moft of the two Tubes fixt to the fame place , fo as ftill to 
refpeft the fame point or beginning of the Divifions upon 
the Boards or Une s by the help of the Rod to turn the Screw 
or Rowl) till you find the upper Tube to refped the firft mU 
nute, and then the firft degree , and fo till you fee the laft mi- 
nute of the five whole degrees , or whatever Angle ejfe you 
defign it to take in ; then (for the firft and third way) reckon 
how many whole Revolutions, and what part of a Revo!u« 
tion goeth to make up that whole Angle , and fubdivide the 
fame by a fmall Table into Minutes and Seconds, and yot* 
will prefently find by the Trial, that you will be able to di- 
vide to a ftrange accuratenefs upon t,hofe Boards, by the help 
of your Tubes and &mp,even at the diftance of 1 ooo, r 500, 
or 2000 foot, and even almoft to equalize the Divifions by 
your Comfdffes , when at the very Boards. And by this you 

C 2 may 



( 12 ) 

may eafily examine, whether your Inftrument doth make the 
fub-divijions exaflly or not, which will be a great confirma- 
tion of the certainty and truth of your Inftrument. But for 
thefecondway, by ftreight Screws , the Table of Subdivi- 
fion into degrees, minutes, and fecwds, mu ft be proportioned 
according to the length of Subtenfes anfwering to the Radm 
which is the dilhnceof the centre of the Renters from the cen- 
tre of the Inftrument. 

Now, becaufe in an Inftrument of this bignefs it will be 
fomewbat troublefome to turn the whole Angle by the help of 
the Screw upon the Limb , which I findalfo is fomewhat 
troublefome in the Inftrument of three foot Radm, when the 
Angle is large, therefore for preventing of that trouble, and 
to be able immediately to open the Inftrument to the Angle 
deflred,or very near it. The Screw /(in the firft Figure of my .4- 
mmadv.)dit the end of the moveableArm,is made,by unfcrew- 
ing, to draw offthe long Screw from touching the threds on the 
Limb, which being done , the Arm is at liberty to be moved 
to any part of the Quadrant, when by returning the Screw /, 
the Screw- frame and Screw is brought down again to take 
hold of the Threds of the Limb of the Inftrument. The on- 
ly care to be taken in this a&ion, is, that neither the Index e e 
beatallmoved out of its pofture to the Index-frame h h, nor 
the Index 8 be moved at all about the rod of the Screw 999. 
It matters not at all though the Screw-rod 999 be turned 
round or moved, fo as it be done by the Rod 000, and the 
handle thereof p p , or by the fmall handle x at the end of the 
Screw-rod, and that the Index 8 being very ftiffly fixt to the 
(aid Rod, be moved round with it by the fame motion , with- 
out vary ing its pofition to the Rod 5 for being again brought 
down by the return of the Screw/, to take hold of the 
Threds of the Limb, into which it muft be fteadily guided by 
hand, the Index ee will (hew upon the Limb the number-of 
threds Qt Revolutions from the beginning, and the Index 8 
will fiiew what part of a Revolution there is to be joyned to k. 
I hope I Ihall not need to fpend time to explicate, how 
the Centre of thefe TWw are-to be made, nor how the GlafTes 
and Thred-fights are to be fixt, nor need I much to fhew, how 
the tubes maybe ftiffned to keep them from warping very 

much 5 



much* A fmall matter of warping not creating any fenfible 
errour, I am not much concerned to prevent. 

If it be defiredto make the Screw lefs , and only long e- 
nough to fubtend one whole degree , which is enough in i li- 
ft ruments of fifty or fixty foot Radius , it may be done by a 
ftraight Screw very well , if care beufed , which will very 
exa&ly take Diameters m& Tranjits to a fingle Second. 

Another thing 1 promifed further to explain, was, the 
contrivance of the Arms and Joynt , mentioned in page 73, 
as a Univerfal Inftruoient for defcribing all manner of Dials. 
For adjufting the Hand of a Clock, fo as to make it wove in the 
fhadow of the Style of a Dial, that is, in the flam of the right 
afcenfion of any Point, of the Ecliptick, or of the Heaven ; or. 
fecondly, in the fhadow of a perpendicular, or inclined Style : 
For dividing and defcribing all manner of Ellipfes in any Ana- 
lematical projection 3 and alfo 5 For making all manner of Ellipti- 
cal Dials in z!Mr. Fofter'i way. For communicating a round 
motion through any irregularly bent way, without flaking or 
variation , and the like* 

Firfi^ The Jnfrrument for defcribing all manner of Dials by 
the Tangent projection, muft be made in this manner, defcribed 
in the 1 tth. Figure, in which there are two Axes or rods of 
Wire that are joy ned together by a Joynt, which from the 
applicability of it to, and fitnefs for all kinds of motions 
and flexures, I czMzUniverfal Joynt. One of thefe Rods b b, 
is, by the help of a Frame a a , placed perpendicularly over 
the centre of the Dial , the fharp or pointed end thereof c 
being funk into the Centre, about which it is to be moved ac- 
cording as it fhall be guided by the motion of the fecond Rod 
or hKisdd. This feco«d Rod or Axis, is, by its Frame, to be 
moved and fet fo as to be parallel to the Axis of the World ; 
then the Hand ee of this lafl being turned to the hour of 
Twelve on the Plate//, the Hand of the firftgg will point 
out upon the Dial-plain , the Meridian or Twelve of Clock 



And fo for defcribing any manner of Dial , you have no- 
thing to do but to find thcSubftile , and the altitude of the 
Stile above the Plain, and to put the Axis in its due fcituation 
accordingly, that is, parallel to the Axis of the Earth, and 

then 



C H ) 

then by. the Plumbet at the end thereof to reftifie the Meri- 
dian or Twelve of clock point: For then, by turning round 
the Axis or Rod d d by the handle , till you fee the Index e e 
on the Axis to point ac thofe Hours, halfs, quarters, or minutes 
you have a, mind ,to take riot ice of in your Dia 1 ; by the fecond 
Index.£g, you are directed to the true correfponding poire 
in the Plain of the Dial it (elf.. But in fuch Dials as are in 
or near a Polar- plain, ic will be convenient to make ufe of a 
fmall Thred to extend from the Crofs, till it touch the Plain in 
the feveral hours, halfs, quarters, minutes, &c. The Arms of 
thejoyntin this Operation are to be fo fixed, that the axis 
of the Plate may crofs the axis of the Rod at right An- 
gles* 

The Universal Joynt for all thefe manner of Operations , 
having not had time to defer i be the laft Exercife , I (hail-now 
more particularly explain. It conliiteth then of five feveral 
parts, each of which I (hall defcribe in the 9 and 10 Fig. 

The two firfi parts are, the Rods and Axes A and B , on 
which the Semicircular Arms are^ faftned , which are to be 
joyned together fo, as that the motion of the one may commu- 
nicate a motion to the other according to a proportion , 
which, for diftinftions fake 5 I call Elliptical or Ob- 
lique. 

The two next parts are, the two Semicircular ArmsCC 
and D D, which are faftned to the ends of thofe Rods, which 
ferve to take hold of the four Points of the Ball, Circle, igjflfc 
dium, or Crofi'va the middle, X\ each of thefe pair of Arms 
have two Centre-holes into which the (harp ends of the Me- 
dium are put , and by which the Elliptical or oblique pro- 
portion of Motion, is fteadily, exaftly, and mod: eafily com- 
municated from the one Rod or Axis to the other* Thefe 
Centre-holes I call the Hands, 

The fifth and laft thing, is, the Bug, Round-plate, Cro/l, or 
Medium X in the 'middle, taken hold of by the hands both 
of one and the other pair of Semicircular Arms, which, for 
diftinftions fake, I henceforth call the ^Medium, and the two 
Points n , taken hold of by the Bands of the Axis, I call 
the Feints, and the other two Points 22, taken hold of by the 
fecond pair of Arms, I call the Pivots. 

Fir ft, 



* C 15 ) 

Firft,for the Rods\ they may be made of what bignefs you i 
think (it , according to the ufe for which you defign the In- 
ftrument. The only care to be taken in the making of them, is, . 
firft that they may be exaftly Cylindrical in thofe parts that 
move in Collers , andfecondly, that the Axis or middle line 
of them do cut each other exa&ly in one point 9 which'point 
muft not vary upon any alteration or change of the Joynt by 
bending the angle they make with each other, moreorlefs, 
nor with the inclination of the Semicircular-arms to any de- 
fired obliquity, nor with the rotation or turning round of 
the whole Inftrument. They require therefore a very dexte- 
rous, and a very knowing Artift , to make them as they ought 
to be, to perform their motion with exaftnefs. Let a £ then 
reprefent one of thofe Rods , and c d a fecond , which are 
turned exa&ly cylindrical within the Collers tf/g and #, and 
thefe Collers are fo difpofed and fixed on fome frame, that the 
middle line or axis of both thefe Cylinders may cut each o- 
ther in the point e 5 if then both their necks and collers be 
wrought true and exaft, the Axis or middle lines of them 
willalwaies cut each other in the fame point, howfoever they 
be turned round within their Collers, nor muft this points 
be varied, howfoever thofe two Axes are inclined to each 
other, fo that though c d be infledted to 7 m, or n 0, and fo 
make either an obtuferor acuter Angle, yet the point i muft be 
the centre of the Medium,where both the Axes concur and cut > 
each other. 

Secondly > The SemkircHUr-arms may be made of what 
bignefs, thickn«fs, or ftrength, the occafionfor which they are 
defigned (hall require ; that is., if they are only to carry the 
Hand of a Clock in the flhadow of a Common Dial 9 whether 
made after the Orthographical, St geographical t or Horological 
proje&ion; or if they are by an Annual motion tofhewthe 
motion of the Sun in the Ecliptick, or the equation of Time, 
a very finall ftrength is fufficient 5 but if they are for carrying 
round a great Quadrant , fuchasthat I have heretofore de- 
fcribed , there they muft be made ftronger and more fubftan- 
tial. Care alfo muft be had, that the inclining the Arras to 
any angle may not vary the centre of the Ball or Crofs out of 
the point, where the two Axes cat each other. Both thefe 



C M ) 

Arms are to be made fo as to be inclined to any angle ; that 
is, that the Axis of the Medium , taken hold of by the Arms 
of Iron, maybe made to incline to the axis of the Rod, on 
which they are in any angle defired, and being fee to that 
Angle, to be fteadily fixed , which may be done by a pin, 
fcrew or wedge; the way I make ufe of for the Azimuth- 
lBitrument,defcribed in the up. of my AmmadverftmsM this 
which is delineated and explained in the yth. Fig., where G re- 
prefents a focket of Brafs,movab]e cylindrically round about 
the end or neck B, of the Axis or Rod BE, the fame with a £, 
in the 22 Fig* of my Animadverfions i and fixable in any pofture 
defired, by help of a fide-Screw £, fuch as is very commonly 
made ufe of for moft In ft rum ems that are fixed upon the end 
of a three kgg'd Staff, and is commonly called a Cylinder and 
Soc^et;th\s Socket of Brafs hath a fmall Rod of Iron,£,fixed in- 
to it at k, which is near the middle of its concave part, through 
this Rod there is made a fmall eye or hole , and through that 
hole a wedge-like pin m being thruft, ferves to keep the Semi- 
circular Iron-arms CC, fteady and fixed in any pofture they 
fhall be rectified to. The Semicircular-arms CC, are to be 
made of very good Iron, or rather Steel , and to have a chan- 
nel or grove quite through the middle of one of them, and 
extending the whole length of a quadrant of a Circle, namely 
from n to 0, becaule, according to the variety of occafions, it 
may be varied to any point between n and 0; and 'tis to be 
obferved; that the Iron-rod 4 muft be fo far fixed out of the 
axis of the Socket g , as# is diftant from i, or from p the 
middle of the Iron-arms between i and *, that fo when there 
is occafion, the Centre-hole or hands / may be moved to/> and 
fattned. At q muft be made a joynt in the Semicircular-arms,fo 
that when the end n of the Arms is fixed in or near £,che other 
arm C may fall back from the point / , othervvife the circular 
motion, in many cafes, cannot be continued quite round , and 
communicated from one Rod to the other, by help of the Me- 
dium or Plate x. The feveral pieces of this Joynt, as they are 
apart and diftinft, you may fee in the $th. Figure, and as they 
are joyned all together fit for motion you may fee in the tenth 
Figure, to which alfo the defcription of every partis ad- 
joyned in words referred toby the help of Literal marks, 

which 






( 17 ) 

which, I hope, will make it fufficiently plain to any Artlft co 
.underhand. 

Thirdly, The medium Bali or Crofs X, muft be made ot 
a bignefs fuirable to the Anns and Cylinders , and g»ea. care 
muft be had that all the ends, points, or handles, lie exactly 
'inthefame'pjain, and that they be all equally diflant from 
their Center, at leaft, that any two oppofite ones be fo 
made, becaufe it is notabfolutely neceffary that they fliould 
befoall four, though in mod cafes it be Deft} and farther, 
the Handles or Pivots ought to be exa&ly round, conical, or 
cylindrical , and the middle lines of them to cut each other 
at right angles, or upon a fquare ; and in general, thatall 
things about the faid 'Joync be fo contrived and wrought 
that the Axis of the two Rods may alwaies cut each other in 
the centreof the medium Crofs or Plate , and that the faid 
Centre, whatever change happens to the Joynt , may alwaies 
keep exactly in the fame very point', without any alteration. 

The fliape of this Medium may be either , a Crofs whofe 
four ends hath each of them a Cylinder , which is the weakeft 
way,' 'tis defcribed in the 9 and ioth, Figures by the Crofs X; 
or fecondly, it may be made of a thick plate of Brafs , upon 
the edge of which are fixed four Pivots, which ferve for 
the handles of the Iron-arms to take hold of; this is much 
better than the former, but hath not that ftrength and fteadi- 
nefs that a large Ball hath, whieh is the way I mod approve 
of , as being ftrong, fteady, and hand fome ; thefe are deline- 
ated in the afore faid Figures, by X x, and Xx x. 

If it be an Elliptical Dial to be defcribed by the Ortho- 
graphical projection, the former way for defcribing Tangent 
"Dials, gives the lines that divide the Ellipfis of the Equinox 
in its true proportions ; and if you would have the Lines thac 
divide the Ellipfis of either Tropick , or of any other pa- 
rallel Circle , you muft rectifie the Semicircular Arms CC of 
the Axis B B, to the degree of the declination of that Paral- 
lel , and them proceeding as before, you have the Lines 
which from the aforefaid Circle divide the Ellipfis of that 
Parallel accordingly. Perpendiculars alfo,let fall from the ends 
of the Crofs 1 1 , give the true Ellipfis in the Orthographical 
praje&kn anfwering to that Parallel* 



( is ) 

Thcfe Lines thus found , are the true azimuth Lines of the 
points or divifions of that Parallel, and are this way traced 
out exactly , without any trouble of Calculation , which for 
fome purpofes, in Surveying, Navigation,^ a. are of very 
great ufe, as I (hall afterwards fhew. 

The Univerfality of this Contrivance, for refolving almoft 
all Spherical Queftions , makes it of very great ufe in Navi- 
gation, if it be adapted as it ought to be , efpecially for the 
Common Sea-mans ufe , who, with a very few Rules, will be 
able immediately to find the hour, and a&imuthof any point in 
the Heaven, fufficient ly accurate for moft Obfervations that 
can be madeat-Sea 5 of which more hereafter* 

For making the /Z^' or Indexof a Clock movein theflba- 
dow of the Style, made upon the Face of the Dial , and ex- 
pofed "to the Sun, this Joynt, being made to joyn the arbor 
of the Wheel that goeth round in twenty four hours, with the 
arbor of the hand , performeth it without any other Wheel or 
Pinion in the Dial or Face part of the Clock ; if the Arbor 
of the Clock that fliould have carried the Hand round in 
twenty four hours, be made to have the fame inclination to the 
plain of the Dial that the Axis hath, whether parallel to the 
Axis or not, it matters not at all, fo that the Hand be re&ified 
accordingly as it ought to be, and that the Style of the Dial 
arifeth from the centre of the Dial , out-through which the 
Arbor is produced for carrying the Hand, and placed in its 
Parallel refpeft to the Axis, as it ought to be for a tangent 
Dial. For the fhadow-Line of the Axis upon the plain of 
the Dial, being alwaies carried round the centre of a Dial in a 
plain, which pafleth through thedxu otStyle,md maketh equal 
progrefllons about it in equal fpacesofTirne,and unequal pro- 
grefllons upon the Dial-plain, according to the proportion of 
Inclination, and the whole Revolution being performed in 
twenty four hours, and the Hand of the Clock upon the Face 
of the Dial being alwaies moved in a plain which patfeth 
through the Arbor of the Clock, and maketh equal pro- 
grefllons in equal fpaces about the faid Arbor, but unequal 
progrefiion about the Centre of the Dial , according to the 
differing Inclinations : And thofe Inclinations being both in 
rhe Sun- Dial and Clock-Dial thefame, it will follow, that the 

Hand 



( i9) 

Hand of the Clock muft alwaies move in the fliadow of the 
Style, if the Hand be once reftified to the true Plain, and the 
Axis or Arbor make its Revolution as it ought to do in twenty 
four hours. 

If it be further defired , for the eafe of taking Azimuths 
and Altitudes, that the Arm of the Azimuth quadrant that is 
onccadjufted to the Coelefiial Object, fihould, by the aforefaid 
Joynt or Inftrument, be kept alwaies refpe&ing and follow- 
ing the faid Object in its Diurnal motion , it may be very eafily 
performed by the help of a fmall perpendicular Ruler , whoie 
lower end is Joynted into either of the Arms i r , of the cir- 
cular Plate X, in the 22 and 23^. figure of my Animadver- 
jions, and the upper end joynted into the movable Arm, at 
the fame diftance from the Centre of the Quadrant that the 
lower end is from the centre of the Plate X,and that the centre 
of the Quadrant be fet exadly perpendicular over the centre 
of X; but then the divisions by the helpof the Screw cannot 
be made life of, becaufe the Clock-work it felf is to turn and 
move the Arm: But it may be done by any Quadrant, where 
the minute Divifions are performed by the help of Diagonals. 
For the Arms of the Circular-plate 1 1 being alwaies moved in 
the fuperficies of the Cone defcribed , by the radiation from 
the Cceleftial Qbjeft to the centre of the Plate X, that is to 
fay, the Line that paffes through the Centre of the faid Plate, 
and through the two Points r 1, being alwaies directed to the 
Cceleftial Ob jedt, if the Arm of the Quadrant be moved per- 
pendicular over it, and parallel to it, that alfo muft be aivvaies 
directed to it. And hence it may very eafily be conceived, 
how the aforefaid Semicircular Arms may be readily and cer- 
tainly rectified to any C&leftial Object ; that is, by fixing TV- 
lefcopes or Common-fights upon the Circular- plate , fo as the 
Axis of them may be parallel to the Line through 1 1 , and 
loofing the Screw b to retlSfie it to thepbjeft by the fighr, 
and then immediately tofixitinthe faid pofture by the afore- 
faid Screw 5 the Clock-work of the faid Inftrument having 
been before that put into motion. The reafon of all which 
will eafily appear to any one that throughly confiders, that 
all Celeftial Objeds feem^by the diurnal motion of the Earth, 
to move equally from Eaft to Weft about the Axis of it , and 

D 2 would 



(20) 

wouldalldoexa&ly fo, were they not fomewhat varied by* 
their own proper periodical revolutions, which though it 
doth indeed make a real difference between their velocities 
about the Axis of the Earth, yet that difference is but fmall - r 
and the fame circular rendu 1 tun will ferve both for the Sun, 
saloon, Planets, and Stars, if at lead: the Pendulum p ^ in the 
fifteenth Figure, be a little lengthened or fiiortened 1 , by lifting- 
up or Jetting down the Rod qq> in proportion as^he Body k 
moves fwifter or flower. And 'twill not be difficult to mark 
upon the Rod q q± the appropriated length of the Pendulum 
for the Sun, iMom , or Stars ; but this only by the by. 

If in the next place it be defrred , thac the Hand of the 
Clock fijould be alwaies carried round upon the face of the 
. Clock, in the fhadow of a Style perpendicular to that plain, 
byreafon that the declination of the Sun daily varieth , the 
ang'esof the fbadow about that Style varieth alfo, and con* 
frequently the inclination of the plate of the Joynt to the 
Axisor Arbor muft vary alfo, and that variation muft al- 
waies be the fame with "the variation of the declination of 
the Sun', which is twenty waies mechanically performabb 
in Clock- work , fo that the motion (hall be performed by 
the Clock-work alone, without touching it with the hand. 
All the other directions that are requifite to adjuftthe Clock- 
work to fuch a Dial, is, only to make the Arbor of the 
Glock-workto have the fame inclination to the plain of the 
Dial, that the Axis of the Earth, or a lineparalel to ic hath 5 
and rectifying the Hand into the true plain of the Axis , or 
Inclined arbor, the equality of the motion of the Clock- 
work , according to the diurnal and annual motion of the 
Sun, we fuppofe alfo to be provided for. 

If theHandof the Clock be defired to be moved in the 
ftadowof any other ftreight Style, howfoever inclined to 
-the plain of the Dial , then muft there be another Joynt like 
the former, added to the end of that Axis which was per- 
pendicular to the plain of the Dial, and all the three 
Axes muft be fcituate in refpe&of the Plain , in which the 
Hand on the end of the laft is to move , that the inclination 
of the faid Axes to each other, may reprefent the inclination 
of the Axis to the perpendicular axis of the Plain, and of 
- = " *" H that: 



( 21 ) 

that perpendicular Axis to the axis of the Style. Or, which 
is fomewhat fhorter, and may be made handfome enough , Let 
the two ends of the Hand reprefent the two points of the 
fecond circular Plate or Globe , extended long enough to 
reach to the hour Circle , then let the axis of this fecond 
Arm be placed in the axis of the inclined Style, and lee the 
axis of equal motion , reprefenting the axis of the diurnal 
motion of the Earth, be placed with fuch inclination to it, 
as the axis of the Earth hath to the oblique Axis or Style of 
the Dial, and the motion will be mo ft exactly performed me- 
chanically, and according tathe truth of Geometry and Cal- 
culation. 

Now, in all thefe motions, caremuft be taken, to provide- 
that the inclination of the declination of the Sun from the E- 
quinoctial,be exprefr by the ends ir,in the 22 and 23 Figures 
of the fecond Plate.' of my Anim&iverfum % of the Grofs , , 
taken hold of by the femicircular arms c d, upon the end of 
thefirft Axis ; that is, that the faid arms may, by their revo- 
lution, make the line of the Crofs defchbe fuch a cone about 
the firft- Axis, as the motion of the Sun doth about the axis 
of the Earth, making the centre of the Earth the apex of that 
Cone $ which will be done, if the faid femicircalar Arms be 
moved, and fet to the declination of the Sun for that day. 
Or, that an additional motion be added to the firft: Axis, 
that the Clock it felf may perform it* This may be done 
twenty waies eafily enough , which I fuppofe will be fuffi-. 
ciently obvious to any knowing Mechanick , and that with- 
out the help of Tooth-wheels or Pinions, which in works of 
this nature are in no wife to be made ufeof, by reafon of their 
iliaking and uncertainty, which I fliallelfewheredefcribe* . 

There is one only difficulty in this motion,, and that is only 
in fuch Obje&s as pafs over, or very near the Zenith or Nadir 
of the place, for in thofe cafes, when the Object comes very 
Dear the Zenith , the obliquity of. the motion of the one to 
the other is fo very great ^ that the (irft Axis doth not move 
the fecond without fome difficulty : But to remedy this, the 
expedient is as eafie, and that is , by having a liitle barrel 
about the perpendicular Arm, to carry it forward as far and I 
asfaftasthefirft Inclined axis will permit it *, which weight ~ 



C 22 ) 

may be removed as foonas the Qbjed: is a little way paft tte 
Zenith. 

The next ufe that may be made of this, is, for carrying the 
Hand of a Clock fo, as alwaies to move over that point of 
the Ecliptick in which the Sun is, in a Stereographies! 
projection of the Sphere upon the Plain of the Equinoctial, 
or in an Orthographical projection of the faid Sphere upon 
the fame Plain, fo as to exprefs thereby not only the differing 
right afcenfious , but the anotpaly alfo of the Suns motion in 
the excentrick of the Ecliptick. And by this means the. 
Face of the Clock may be made by a Flanifpherical pro- 
jection, to reprefent the motion of all the Stars appearing 
in any Horizon that is not too near the Equinoctial , their 
Ri flags , jet tings, cttlmlnatings , azimuths, and almicauters ; 
Ktjings and fittings of the Sun, the lengths of the Days and 
Nights, and of the Twilights and D awnings , and many other 
Problems of theSphere. And,which is a confequenc of this, 
it may be made to fhew the equation of Time, which isne- 
ceffary to be made ufe of for fetting a pendulum Clock by 
the Sun, the manner of doing which I mult refer.to another 
opportunity, as I muft alfo the ufe of this Joynt, for draw- 




and Conoetdical\ all manner of Foliage and Flower-work \ all 
variety of Basket or Breaded-work , all variety of Spiral and 
Helical-work Serving for the imitation of the various forms and 
carving* of all forts of Shells; for cylindrical and conical Screws^ 
aH variety ofEmhofiments and Statues s all variety of edged and 
Wheel- like work ; all variety of ' Regularly Jhaped Bodies, whe- 
ther the five Regular bodies of Blato, or produced from thofe 
by various fecliOBS or additions, of which the variety is in- 
finite^ all variety of bended Cylinders or Cones , and thofe 
whether round, in the manner of an Oxes-horn , or compref- 
fed and angular, like thofe of a Bam or Goaf, for all manner 
of Swafht-work, Cempreft-work , &c. every of which prin- 
cipal parts hath a vaft variety , and the compound and 
decompound principles have a variety almoft infinite. 

Appen- 



( 2 3 3 

Appendix, 

Concerning the Eclipfe of the Moon 
obferved in London. 

TAmary the firft, 167?, being at Sr. Jonas Meres in the 
Tower of London, and making ufeof a Teiefcope of eight 
foot, and my pocket- Watch, whofe bal lance was regulated 
with fprings, I obferved the Eclipfe of the Moon, which 
began at about twenty minutes after five , the penumbra very 
much cheating the naked eye 5 for tr;e Penumbra had darkned 
that fide of the Moon, next the fpot Grimaldi , about half an 
hour before, and grew darker and darker towards the edge 
where the Umbra erttred, fo that if the light of the Moon were 
dimtniflied either by refle&ion upon dark Glafs ,. or looking 
through a final 1 hole, between a quarter and a third part of 
theMw#feemed eclipfed before the Umbra entred} but the 
Teiefcope difcovered it plainly to be no true umbra, but 
penumbra. 

This I note, becaufefuch Perfonsas do not make ufe of a 
Teiefcope, but only of their naked eye, are very apt to be 
much deceived in their eftimation of the beginning and end 
of the Eclipfe.. 

At$» 48 we judged by the Teiefcope that the Moon was 
eclipfed fix digits, or half; at 6. 19. the total Eclipfe began, 
when the Moon appeared of a very red colour , efpecially 
towards thatpartof the Limb where thedired Raies left it, 
which was at the MareCrifium, which is pppofite to Grimaldi 
Now the Skie being fomewhat clearer ,; it being before haz)v 
with the Teiefcope I began to difcover a great number of 
finall Stars about the Moon, which appeared yet much more 
confpicuous , after J had taken off the apperture from the 
ObjecVglafs , and . amongft the reft, one feemed very confpi- 
cuous, and Jay in the way of the Moon :, which I diligently 
watched and obferved , that it was j aft covered by the <tMoon 
at 6 h .47'* so'/, the 'MvmSxHt covering it with that part of it; 

which 



C 24 ) 

which was almoft perpendicularly under the centre of rile 

About three quarters of an hour after the total iminerfion, 
the body of ihe Moon was exceeding dark , and almoft un- 
^perceivable , -being then near the centre <3f the -Umbra , and 
afterwards the Eaftermoft or foremoft pare of the Limb of 
xheMoon began raise inlightned, whereas before the Weftev- 
1110ft Limb had been the brighteft. This Was alfovery no- 
table , that that -part of the oJMoon that was towards the 
North-Pole, a pretty while before the emerfion of the Moon 
.out of the total Eclipfe , and even till the very emerfion, and 
Xomewhatafcer too, appeared inlightned with a much brisker 
light than any other pare of the body , except that which 
was next the Limb where the light again emred. From what 
i-caufe this fhould happen, I know not ••> poffibly it might be 
.caufed by a greater refracVionof the Air near the North- 
Pole of the Earth, and I am much troubled, that I had not 
taken notice whether the like, phenomenon had not happened 
to the body of the Mow before it had paft the centre of the 
Umbra. It was very manifeft, that there was a confiderable 
quantity of light' that kept that Limb of the Moon which 
was next the light, confpicuous by the Telefcope all the time 
of the total Eclipfe, and 'tis very rational toafcribe it to the 
Raiesof the Sun, refracted by the Air, or atmofphereof the 

Earth. 

I was very well plea fed to obferve the Moon to cover 
Several final 1 Stars that lay in its way , but I kept no 
account of them, but only watched diligently when the Star 
that entred behind the Moon at 6. 47. 30. would come out 
again, which I found it to do at 7-3 '- feeing it at the very 
moment of time that it began to appear again. And it was 
alio at the fame inftant discovered by SwJmos More, who was 
.expeding.it with another Tribe. 

At. 7*. 3% the body of the Moon firft emerged out of the 
Umbra at the fpot Grimaldi y and foon -after all thofe fmall 
Star j that were confpicuous before about the body of the 
Moon, vanifhed. However I had , before its fkft emerfion 
our of . thefliidow, taken a little draught of the fmall Stars, 
according to their feveral pofitures and magnitudes , only by 

guefs, 



C,25) 

guefs, that I might a week after, when the Moon was gono 
farther off, inquire what that Star was that had fuffered fo 
confpicuousan Eclipfe, and that thereby J might the more 
certainly determine the true place of the Sun and &loon ac 
thatinftanr, which I found to be that in Buyer, touching the 
Ecliptick, in about 2 ,.. 4 o\ of Cancer. The Umbra ceafed 
wholly at eight of the Clock and five minutes, though the 
ftnumbra then poffeffed almoft a third of the Moons Diame- 
ter, and lafted near half an hour after, before that fide of the 
Mom was perfectly mlightened like the other. 

There was one Phenomenon very remarkable.which I>ook 
moreefpecial noticeof, as feeming to me very confiderable 
for the determining that controverfie, whether the Moon have 
an atmofphere or not, like that of the Earth ? And that was 
that after the OHoon was entred wholly into the Umbra of the' 
Earth, that part of the Limb of the Ofam which' was Ialt en- 
lightned, continued for a confiderable while to have a very 
great brightnefs upon it, which extended on each fide that 
part of the Limb, both northwards and fouthwards toa- 
bout aquadrantof the Ohons Limb.making a reputation 
almoft of a New Moon about a day or two old, and as the 
body of the Moon ; was immerged deeper into the ftado w, fo 
this brightnefs or light grew fainter and fainter.but ftill fee„> 
ed to fpread it felf very far upon the Limb of the Moon only, 
and not upon the body thereof. That which was fpread in- 
to the body being much fainter and weaker, and feeming fas 
I before noted) to proceed from the refraflion of the Atmof- 
pheres of the Earth. Nor was this only confpicuous at the 
A&^entnng into the total darknefs, but as remarkable a!fo 
at the exstus thereof out of the fame, infomuch that fame of 
thofe Perfons who at the fame time viewed the fame with 
me, verily believed the Moon was not wholly eclipfed fo 
foon as real y it was, nor continued fo long in ,hat obfcurity, 

asveryv,fibly,td,dbythefpaceoftwoorth r eeminuces.For 
Itookefpecial notice when this inlightningof the' Limb be- 
gan again to appear, and 1 obferved its mcreale, and fpread- 

Kl?Ti t Umb ' M thever y in^nttbat the immediate 
light of the Sun touched the very extremity of the Limb it 

E felf, 



fblf, which was indeed fo very briskly bright and ftrong, 
that it did noc only foon make the other light difappear, but 
alfo all the Telefcopical Stars that were near to it, and to- 
wards the end alfo many of themoreconfpicuous Stars, ef- 
pecially fuch as were not far from the body of the Moon. 



t* ii i i'iu b 




t. 



Should have here taken leave of my Reader for this time, 

but that finding in the Tranfattions a paffage inferced out 
of the French Journal de Scavans, about the invention of ap- 
plying a Spring to the BcdUnce of a Watch, for the regulating 
the motion thereof without at all taking notice that this In- 
vention was Jtrjl found out by an Engliji-xmn , and \ovigfime 
publifbed to the World: I rnuft beg the Readers patience, whi lft 
J in vindication of my own right againfr. fome unhandfome 
proceedings, do acquaint him with the ftate of this mat- 
ter. 

About feventeen years jince, being very inquifitive about 
the regulating the meafure of Time, in order to find the Longi- 
tude, I did from an Art of Invention, or mechanical Algebra 
(which I was then Matter of) find out and perfeft this con- 
trivance, both as to the Theory and Experimental verificati- 
on thereof,of which I then difcourfed to divers of my Friends, 
but concealed the modus. 

About fifteen years fmce, to wit, in the year 1660, pre- 
fently after his Ma jetties happy Reftauration, I was in treaty 
with feveral Perfons of Honour (fome of which are yet li- 
vings though one of them is Jince dead, but I have fufficient 
evidence to produce in his own writing that he wasonejfor 
the difcovery thereof, upon propofed Articles of encou- 
ragement. This lean prove by undeniable WitnefTes yet li- 
ving, and I have frill all the Papers, Articles, and Tranfadtions 
of this matter by me, in their own hand-writing. 

In 



( *7 ) 

In order to bring this Treaty to'paft , I was Receffiea- 
ted to difcover fomething of Invention about meafuring 
Time, which was, this way of applying Springs to the arbor 
of the Ballance of a Watch, for the regulating the vibrations 
thereof in all poftures. And this I did, to the end that I 
might gain fomewhat of belief in thofe Noble Perfons (with 
whom I was to treat) That I had fomewhat more than or- 
dinary, and was not one of the heard-of Pretenders to that 
Invention: which effect it had, and their Treaty with me 
had finally been concluded for feveral Thoufand pounds, 
had not the inferting one Claufe broke it off, which was, that 
if after I had difcover ed my Inventions about the finding the 
Longitude by Watches, or other wife (though in themfehes fuf- 
ficient) They, or any other Perfon jhould find a way of impro- 
ving my Principles, he or they jhould have the benefit thereof 
during the term of the Patient, and not 1.^ To which Claufe 
I could no waies agree, knowing 'twas eafie to vary my Prin- 
ciples an hundred waies, and 'cwas not improbable but that 
there might be made fome addition of conveniency to what 
I fliould at firft difcover, it being facile Inveniis addere. 
And judging it moft unreaibnable to be deprived of the 
benefit of my Inventions, in themfelves fufficient , becaufe 
others might vary them, or any other ways improve them, 
of which it was very probable they would have no thought s 
if they had not the advantage of being intruded by my 
difcovery,it having lain hid fome thoufands of years already, 
as indeed the e€e& hath made evident and cerrain , there ha- 
ving been nothing done by any body elfe upon that matter 
for thefe fifteen years. 

Upon this point our Treaty was broken off, and I con- 
cealed the farther difcovery of any of the other morecon- 
fiderable parts of my Inventions, for the regulating of Time- 
keepers, as hoping I might find fome better opportunity of 
publifhing them together with my way of finding the Lon- 
gitude of Places, for which I hoped to have had fome bene fie 
for all the labour, ftudy, and charge I had been at for the 
perfecting thereof. Upon this I was told, That J had better 
have then difcover ed all, fince there were others that would find 

E 2 it 



( 2% ) 

h M within fix months ; to which I anfwered, that 7 would 
try them one [even years $ and it is now above twice feven, 

and 1 do not find it yet found out. indeed Mr. Hugenshzxh 
made ufe of that part I difcoveredyand fomewhat Mr. Leib- 
nitz hath hit upon, but both of them are imperfect as I fiiall 
hereafter fhew. 

'Tis true, I was alarum'd by one of thofe Perfons about 
two year s after that, who told me, that he had news that the 
Longitude w^s found outbya l Perfon of Honour ', by away of 
carrying Mr. Hugens'j Fen dulum- Clock, at Sea, kythehelpof 
a Bail and Socket) hungto the finder fide of ^ the Deck of a ship. 
But having adefcriptionof it, I prefently told that Perfon, 
That that Indention would do mine no harm ; and indeed we 
experimentally found it ufelefs to thateffe6 not long after, 
upon a trial made of carrying the faid Clocks off to Sea in 
one of His Majefties Fleafcre- Boats, in the year 1662. 

The Invention indeed in it felf was ingenious, and did 
much more than what Mr. Hugens did expefl, as I was then 
informed by the Right Honourable the Earl of Kincardine, 
the Author and perfetfer of that part of theTnverition. But 
wanting a little addition (which I concealed, and Mr* Hu- 
gens hath not got yet that I hear of J it failed of theefTeft 
that was expected. Notwithftanding this, It was not long 
after publiflied in Low Dutch, and prefently after in 
Englijb 5 wherein what made for it was related, but 
what made againft it was concealed, though they were both 
equally known. 

But on the otherfide, all that I could obtain was a. Cata- 
logue of Difficulties,/^/?, in the doing of it , fecondly, in the 
bringing it into publick ufe, thirdly, in making advantage of 
it. Difficulties were propounded from the alteration of 
Climates, jiirs, heats and colds , temperature of springs, the 
nature of Vibrations, the wearing of Materials, the motion 
of the Ship, and divers others. Next, it would be difficult 
to bring it to ufe, for Sea-men knew their way already toany 
Port, and Men would not be at the unneceflary charge of the 
Jfparatus, and obfervations of the Time could not be well 
made atSea, and they would nowhere beof ufe but in Eafi 

and 



C *9 ) 

and Weft India Voyages, which were fo perfectly under- 
flood that every Common Sea-man almoft knew how to Pilot 
a Ship thither* And as for making benefit, all I'eople loft by 
fuch undertakings ; much had beentalkt about the Premi- 
ums for the Longitude r but there was never any fuch thing, 
no King or State would #ver give a farthing for ir, and the 
like 3 All which I let pafs* 

At the earnefti importunity of a Dear Friend of mine, 
fince deceafed, I did, in the year 1664, read feveral of my 
firft Cutlerian Leftures upon thatSub;e#, in theopen Hall 
at Grejham Col ledge, at which were prefent, befides a great 
number of the Royal Society, many Strangers unknown tome, 
I there (lie wed the ground and reafon of that application 
of Springs to the Ba/lance of a Watch, for regulating its mo- 
tion , and explained brieiy the true nature and principle 
of Springs, tofliew the Phyfical and Geometrical ground of 
them* And I explained above twenty feveral ways by 
which Springs might be applied to do the fame thing, and 
how the Vibrations might be fo regulated, as to make their 
Durations either ail equal , or the greater flower or quicker 
than the lefs , and that in any proportion afligned. Some of 
thefe ways were applicable to JefTer Vibrations, others to 
greater, as of 2, 3, 4, 5, 6. or what number of Revolutions 
weredefired ; the models of which I there produced, and I 
did at the fame time (Lew wherein the aforefaid Sea-Clocks 
were defective. 

All thefe particulars alfo were at feveral other times , $c 
the Publick meetings of the Royal Society, difcourfcd, expe- 
rimented, and feveral Models produced. I did alfo, at the 
earneft defireof fome Friends , in theyear it 64 and 1665,. 
caufe fome of the fa-id Watches to be made, though I was 
unwilling to add any of the better applications of the 
Spring to them , as waiting a better opportunity for my ad- 
vantage. 

Of all thefe things the Publiftier of the Tranfatfions was 
not ignorant , and I doubt not but Mr. Hngens hath had arj 
account, at leaft he might have read fo much of it in the~ 
Hiftory of the Royal Society as was enough- to have given him 

notice 



( 30 ) 

notice of it, for page 247 of that Hiftory, aroongft other Ex* 
perimented Inventions, there are recounted feveral new ways 
of Pendulum Watches for the Pocket , wherein the motion is 
regulated by Springs, &c. The account of the feveraJ ways 
was given fomewhat larger to the Learned Author of that ex- 
cellent Eiftory, though he, as judging ic more proper to his 
defign , was pleafed to give only this fummary account. 
Mr. Hugens might therefore , if he had pleafed , have men- 
tioned iheftrft Invent er ^ Nam ingenuum eft fateri; as he 
might alfo-that of the Circular Pendulum, which is menti- 
oned in the fame page of the aforefud Hiftory. 

But though he would not pleafe to confefs he knew my 
publifhed Invention, yet / am Jure he hath manifested , that 
he knows no more than what 1 had formerly difcovered 3 he 
Having not in leafr mentioned the othe Contrivance , which 
is the principal , and without which the firft part of the 
Invention is bur lame and imperfedt, and doth but limp on 
one leg, and will fomerim^ hobble 1 , and (tumble, and frand 
/till. And the faid Watches will not betres Jufle,wY fliew 
the Longitude at Sea or Land, but, on the contrary,they will 
be fubjeft to mofr. Inequalities of motion and carriage, and 
wirhmany of thofe motions will be apt to ftand (till, what- 
ever to the contrary is affirmed in the French Journal , or in 
the Englifh Tr an fall; ions. 

I forbear now to mention any further the carriage of the 
Writer of the TranfacJions in this Affair, and begging my 
Readers excufe for this digreffion, I fball conclude this 
Trad with a fhort communication of the general ground of 
my Invention for Pocket-Watches, thenumber of particular 
ways being very great, which (that the true Lovers of Art, 
and they only may have the benefit of) I have fet down in 
the Knherfal and Real Character of the late Reverend Pre- 
late, my Honoured Friend Dr. JohnWilh^ns, Lord Bifhop 
of C/?^r,deceafed. In which 1 could wift, that all things 
of this nature were communicated , it being a Character and 
Language fo truly Philofophical , and fo perfectly and tho- 
roughly Methodical, that there feemethto be nothing want- 
ing to make it have the utmoft perfection, and higheft Idea of 

any 



C 3' ) 

any Charafter or Language imaginable, as welf for Philofo- 
pbical as for common and conftant ufe. And I have this fur- 
ther to defire of my Reader, who will be at the pains to deci- 
pher and underftand this defcription , that he would only 
make ufe of it for his own informauon,and not communicate 
the explication thereof to any that hath not had the fame 
curiofity with himfelf. 

This I do, not fo much to hinder the fpreadingof this 
Defcription here delivered, as to revive, and, if poffible, 
bring into ufe and praftice that excellent Defign : It being a 
Character and Language perfedly free from all manner of 
ambiguity, and yet the moft copious, expreffive and figni- 
ficativeof any thing or Notion imaginable, and, which re- 
commends it moft to common ufe, the moft eafie to be under- 
ftood and learnt in the World, see Table the third. 

To fill the vacancy of theenfuing page , I have here ad- 
ded * decimate of thz cent efme of the Inventions I intend ta 
publifh, though poflibly not in the fame order, but as I can 
get opportunity and leafure; moft of which, I hope, 
will be as ufeful to Mankind, as they are yet unknown and 

new, 

1. A way of Regulating all forts of Watches or Time- 
keepers, fo as to make any way to equalize , // not exceed the 
Pendulum-Clocks now ufed. 

2. the true Mathematical and Mechanichal form of all 
manner of Arches for Building, with the true butment neceffary 
to each of them. A Problem which no ArchiteBonick Wri- 
ter hath ever yet attempted , much lef> performed, abece 
ddcceee f gg i'tiiiiii llmmmmnnnnnooprr sssttttttuuuuuuuux. 

3. the true theory of Elaftieity or Springinefs, and a par- 
ticular Explication thereof in fever al Subjetfs in which it is to 
he found\ And the way of computing the velocity of Bodies 
moved by them, c e i i i n s s s 1 1 u u» 

4. A very plain and practical way of count erpoifing Li- 
quors, of great ufe in Hvdraulicks. Difcovered. 

5. Anew fort of Objetf-Glaffes for Telefcopes and Mi- 
crofcopes, much outdoing any yet ujed? Difcovered. 

6. A 



( 3* ) 

6. A new Selenofcope, eafie enough to be made andufed 
whereby the fmallefi inequality of the Moons fur/ace and/mi 
may be moft plainly diflinguifbed. Difcovered. ' 

7. A new fort of Horizontal-Say Is fir a Mill , performing 
the moft that any Horizontal* Sayls of that bigmfiare upable $& 
and the variom ufe of that principle on divers other oseahm, 
Difcovered. 

8. A new way of Vott-Chzrnot fir travelling far, without 
much wearying Horfe or Rider. Difcovered. 

9. A newfortofVhilofophxcdX-Scdes, of great ufemEx- 
per/mental Pbilofophy. cdeiinnoopsssrtuu. 

10. A new Invention in Mechanicks of prodigious ufe, ex- 
seeding the chimera's of perpetual motions for fever at ufe$. 
a a aaeb cc ddeeeee egiii J mm mnnooppqrrrr i 
ttt'uuuuu. . 

aaeff hiiiillnrr sstuo. 



F I N 



J 



ah. II 




LA 






o<K, 

SCRIPT IO 



OF SOME 



Jflecliattwal grmpjotjements 



o F 



Lamps & Waterpoifes- 

Together withfome other 

PHYSICAL and MECHANICAL 

DISCOVERIES. 



MADE BT 



l OB ERTHOO 

Fellow of the 2{oyal Society, 



LONDON, 

Printed for John Marcyn y Printer to the Royal Society, at. 
the Bell /'##. Paul's Church-yard. 1677. . 



♦ . 



CO 
L <Mf M <P J S: 

OR, A 

D E S C R I P T I O N 

OF SOME 

Mechanical Improvements 

LAMPS. 

[He Hypothecs of Fire and Flame I did 
about eleven years fince publifh in 
the 16. Obfervation Pag. 103, '104, 
and 105. of my Micrcgraphia, which 
hath To far obtained, that many Au- 
thors have fince made ufe of it, and 
L aflerted it$ nor have I yet met with 
one confiderable obje&ion againft Jf. 
It (hall not therefore be my bufinefs at prefent to dif- 
courfe of, or farther explain that Theory,which any one 
upon a Arid inquiry into, I queftion not, will find caufe 
fufficient to confirm himin, but rather to mention fome 
pleafant and beneficial ufes thereof; and to hint fome 
Mechanical contrivances for the fupplying the Pabulum 
Oyl or Spirit by the fame Degrees by which it is confumed 
in the flame of a Lamp, that great diffolvent. 

I do not here defign to fhew a way how to make a per- 
petual Lamp, that being a Ghimera which my Hypothe- 
fis of flame doth feem to deftroy, for the diflblvend muft 
in time be diffolved : But to (hew a wav flow to make 

B J the 




the Receptacle of a Lamp in fuch manner as that it (half 
continue to fupply the Pabulum to the flame equally and" 
for a very longtime till it be all confumed. The con- 
fideration of which Problem firft put me upon the en- 
quiry after a counterpoife for Liquors or Fluids, which 
is alfoofvery great ufe in Hydraulicks, as. Khali here- 
after have occafion to manifeft.. 

This lean do by .very many contrivances^ depending 
from very differing Principles, all and every of which 
maybe fitted fo as to fupply the Oyl or Pabulum of the 
Lamp in luch quantity, and after fuch manner and pro- 
portion as fhall be defired. Khali now omit all the other 
ways of performing this erTecV though divers of them 
are as much or more confiderable than any of thefe I 
here mention. And having promifed in the 52 Page of 
my defcriptionof Heliofcopes to publifh a Counterpoife 
for Liquors, I fhall only explain feveral ways by the help 
of thefe Counterpoifes to do whatfoever can be required, 
as to the manner and quantity of fupplying Oyl to the 
fjame. 

The chief defign of the Counterpoife in this inquifiti- 
on is to keep trie Superficies of the Liquor ( whether 
Gyl, Spirit of Wine, Oyl of Turpentine, or the like ) 
whatever quantity there be in the Veflel, always to the 
fame height, fo that the faid Pabulum fhall always be 
equally diftant from the bottom of the flame, and the 
Wick or flame being once placed at a convenient height 
ordiftance above the Superficies of the Oyl, fhall not be 
deferted by the faid Superficies till the whole quantity be 
confumed} but it is as eafie to contrive it, to fiipply it by 
decreasing or increasing degrees, which are conveniences 
that none of all the Lamps I have ever yet met with have 
had, that was tolerable for ufe. The molt ingenious is 
that which is commonly known by the name of Car- 
dans Lamp, as being published and very probably inven- 
ted by Cardan, which doth-fn fome manner fupply the 
wafting and decay of the Oyl caufed by the flames Con- 
ftirription. But thenit is fubjeft to a great many incon- 
veniences. 



C3) 
veniences, which make it intolerable and difufed : The 
firft is, though it doth fupply the defers of the Oyl to 
the Wick, yet it doth it notconftantly and equally^ but 
byftartsandgluts, for after the receptacle by the Wick 
is filled, the Superficies of the Oyl continues to fink by 
degrees a confiderable fpace below the flame, before 
there be any more (upply added from the great Magazine 
or Repofitory,and till the Air can break in, (which it doth 
very unequally ) fothat there fometimes comes downfb 
great a quantity that the receptacle is over-filled, and 
the flame extinguished, and thefe gluts are more unequal 
the bigger the Magazine be in proportion to the Recep- 
tacle by the flame, and the more the quantity of the 
Oyl be that is fufpended, and the more the Air fpace be 
above the Oyl, and the more tenacious or fluggifh the 
conftitution of the Oyl is. 

The fecond inconvenience of Cardans Lamp is that the 
Air is apt to rarifie it with heat, fo as fometimes to drive 
down fb much Oyl as to overflow the receptacle, and 
choak the flame. 

The third Inconvenience is, that the Wick by the fink- 
ing of the oyl doth fooner decay the flame,being fometimes 
a little higher and fometimes lower upon the Wick 5 for 
if the Wick rife up into the hollow dead part of the 
Cone of the flame, the dreams and coals of the Oyl will 
be fb caked together as to dead the flame and much to 
diminilhthe light and heat thereof, whereas if the Wjek 
be but (hort, and fuffered only to go but a very little 
within the under-Superficies of the flame, it will not be 
fb flopped and caked with thofe feculencies. The reafbn 
of which is evident, for the flame, as I formerly proved*, 
being nothing but the parts of the Oyl ratified and raifed 
by heat into the form of a vapour, fmoak, or fteam, the 
free Air that incompafleth this fteam keepeth it into a Cy- 
lindrical form, and by its diffolving property preyeth 
upon or diffolveth thofe parts of it that are outwards and 
next to the Air, fo as by the faid diflblution it continueth 
the heat, and produceth the light which we obferve$ but 

B 2 thofe 



m 

ihofe parts of the- body of fteam's that rife from the Wiclg 
which are in the middle, and not contiguous to the out- 
ward Air, are not dilTolved or turned into fhining flame, 
by the Air till they rife towards the top of the Cone of* 
flame where the free Air can come to reach, and fo to dip 
folve them, and thence gathering about the Wick in the 
Center of the Cone of flame they choak, clog, and 
quite ftifle it that the flame will quickly go out. That 
this is lb, any one may eafily find if he examine the flame 
of a Lamp or Candle by the help of apiece of glafs: 
For by the tranfparency thereof he will plainly perceive 
that all the middle of the Cone of flame neither {bines 
nor burns but only the outward Superficies thereof that 
is contiguous to the free and unfatiated Air,, and that the 
middle parts may be colle&ed in the form of Soot, or. very 
fine powdered coal dufbi 

Take then a piece of s Glafs, whether Window-Ola^ 
Looking-glafs Plate, or the fide of a Viol, it matters not, 
or, which is. bell: of all, a thin Plate of Sdenitkox Mufco- 
w'^Talk, and hold it Horizontally in the middle of the 
flame, Fo as to cut oft the top or upper part of the Cone 
thereof, then prefently, before it be choaked with (oot> 
look down upon it, and you (hall plainly fee that all the 
middle parts of the Flame and the Wick have no ftiining 
power or light at all 5 nor are they diffolved by the Air, 
but remain in the form of Soot, but that only the Super- 
ficies or outfide of the faid Cone doth burn, fhine, and 
coniume into and mix with the ambient Air. 

In the fame manner,, if you hold the Glafs. or Selenitis 
perpendicularly, and apply the fide of it fbasto cut the 
flame^er axincon^ that the Air cannot come to one fide 
thereof, you may plainly perceive that; the fliining part 
of the flame is. only that which is contiguous to, and 
preyed upon by the free and unfatiated Air, and that 
where that Air cannot come free without being glutted 
and fatiated in its. way, there neither the conlumption of 
theOyl,nor the heat and light of the flame is produced, 
but only a footy, choaking, and ftifling fubftance. 

To-; 



(5) 

To make then the reafon of the Phenomena obferva- 
blc about the lading or (lifting of the flame of a Lamp 
the more clear and eafie to be underftood and compre- 
hended, give me leave to explain the manner of its pro- 
duftionand continuation by a Scheme, delineation, and 
defeription thereof. , , . n 

Let A A then-ill the fecond Table reprelent a body of 
Oyl, or any other combuftible fluid fub(tance,the Superfi- 
cies whereof B B isHorizontal, and pretty near plain. [ I 
fay, pretty near, becaufe it is always either Concave, or 
Convex, more or lefs according tofeveral cireumftances - 
to wit, the capacity and the nature of the Veflel EE, in 
which it is contained g for if the Veflel be fmall, and that 
the Oyl hath a greater congruity with it than^ the Air, 
the Superficies of the Oyl will be very much concavated 
efpecially towards the fides of the Veflel as at C C 5 but 
if the. Veflel beincongruous to Oyl, the Superficies will 
be Convex as at D D, the reafon of which I have long; 
fince explained in another place. ] 

Let FFthen in the third figure reprefent the Wick,, 
which confiftsof a great number of very fine Cylinders or 
hairs of Cotton f f f twifted and laid very clofe together, 
into, and between which the Oyl ( having a very great 
congruity therewith) doth readily infinuateit felf and ad- 
here, and is by the prefiure of the. Air (much greater 
without than between thofe Cylindersor hairs)forced up 
to a confiderable height between them, ( as to the height; 
of an inch and half, or two Inches ) and if by any means, 
the Oyl be taken out at the top thereof, the remaining 
part of the Oyl in the Veffel will afcend to fupply the va- 
cancy of the part drawn off, which is evident in Filtra- 
tion. About the fides of this Wick the Oyl will be fure 
to afcend, and the Superficies thereof will be concava- 
ted as at GG, becaufe unlefs there be a congruity be- 
tween the Oyl and the Wick there will be< no afcent of 
the Oyl therein, and therefore that fubftanee that the 
Oyl doth not readily adhere to cannot be a fit material for 
that purpofe. 



CO 

Now to this Wick thus filled with Oyl apply the 
aflame of a Lamp or Candle, or any other fubftance ex- 
tremely hot, as a glowing piece of Iron, Copper, or the 
like, and by this means the parts of the Oyl in the Wick 
will be^ery much heated , and expand themfelves in va- 
pours into the contiguous Air by thefteams »hhh h h,and 
rill all the Ambient fpace of the Air HH therewith 
which vapours being very much rarified, and confe^ 
quently lighter than theincompaffing Air,are by the grea- 
ter gravity and preflure thereof carried upwards by the 
Curve Lines h i k. Thefe at firft guffi out of the Wick 
at Right Angles, but by the protrufion of the Air are 
quickly turned into a kind of Parabolick Curve hik 
The motion of the Particles in which is fwifteft in kk 
that is to a certain degree of Altitude. The motion of 
afcent increafing fomewhat after the nature of the motion 
of defcent in heavy bodies, I fay fomewhat in that nature 
for if the afcending bodies were uniformly lighter than 
the Ambient they would be the fame, but becaufe the 
,rarefaftion and nature of them is varied by Circumftanees 
therefore it hath but part of that Analogy. 

To proceed then with the Explication : I fay, thefe 
fteams of the Oyl thus afcending, if they are heated 
j?«? fufl ? cient de S ree of heat are preyed upon, and 
difiolved or burned by the Ambient Air 5 which difTolu- 
tion hath this efFeft, firft, that it produceth light 3 next, 
•that it produceth heat enough to make the fucceeding 
parts of the fteams that rufh out of the Wick and follow 
after it to befufficiently heated for diffolution by the Air, 
the heat of which produceth the fame operation upon a 
third, and that upon a fourth, and that upon a fifth, and 
fo fucceffively fo long as there are fteams of Oyl to be 
difiolved, and plenty of frefli and unfatiated Air to 
diflolve. The adion alfo of this diffolution caufeth heat 
fufficient to raife up the fucceeding parts of the Oyl into 
the Wick, and expand them into vapours, and fo to make 
them fit to be further heated and difiolved. It is further 
obfervable in the flame of a Lamp, that thofe vapours 

that 



C 7 ) 
that iffue out of the Wick are by degrees (iiffolved, and 
not all in a moment, for the parts of the flame that ace 
lowermoft about H have a kind of faint blew light until 
they come toT, where they feem to have their brighteft 
and cleareft light and heat,the faid vapours not being hea- 
ted to that degree at their firft breaking out that they af- 
terwards acquire by the farther action of the Air upon 
them. At I they feem to be in their higheft degree of difTo- 
lution, and from thence upwards are made one with the 
diflblving Air, fo that they are not but by other means 
difcernable to the eye of the obferver 5 fo that the fhining 
part of this Conical (haped {pace of the flame is only the 
outride of the Gone, it being that part where the Ambient 
Air preys upon the afcending eruptions of the Oyl, 
namely ,^ where the Chain of fmall Circles intercept the 
Curve lines of the motion of the afcending eruptions. , 

This Figure and fhape of the flame and vapours may 
be plainly feen by the help of a Metalline Concave 
placed at a certain diftance and Pofition, and alfo by ob- 
ferving the fhadow of the Candle caft by the beams of 
the Sun upon a flieet of white Paper, or white Wall, but 
that way of a Concave fyemlum is incomparably beyond 
it, becaufe it crQth fo very plainly ftiew the- form and 
manner of the Iteams rifing. above iiii, as about 
kkkk,&c. 

The Air after it hath performed the a&ion of BifTo- 
lution, and is fatiated and incorporated with the parts of 
the Oyl at ii i, afcend by k k k, but fhine not. All the 
fteams or eruption of the vapours of the Oyl out of the 
Wick fff ftiflne not between the Wick ff'and ii, but 
begin to-be difiblved, and to fhine as they approach 
the frefh Air at ii, where the diflblution is compleated. 

The upper parts of the flame fhine more than the 
lower, the parts having been heated to a much greater 
degree by the longer fpace of paffage they have had 
through the hot Concave part of the flame, and contigu- 
ous or very near to the glowing fides thereof at i i i. # 

All the under parts of the Wick neither fhine nor 

burn, 



(8) 
burrv -but are as it were charkd by the extremity of the 
heat of the Conical Superficies of the flame, they are de- 
fended from burning at the bottom by the frefh accefs of 
new Oyl from the Veflel underneath, and the middle 
parts are defended from burning or fhining by realbn the 
Air cannot approach them before it be fatiated at the 
Conical Superficies i i i by the diffolution of the fteams 
of the Oyl it there meeteth with. But the upper parts of 
the Wick do burn and fhine, if they be high enough, into 
the (mailer, part of the Cone of flame that the Air before 
it be fatiated can reach at them. And if any part of the 
Wick fall into the (aid.Conical and (hining Superficies of 
the flame,it doth both fhine a#d confume, and differs the 
lame diflolution into the Air as the (teams of the Oyl, 
and if any part of this Wick be without this Conical Su- 
perficies at iii, it is prefentlyconfumedand reduced to 
;A(hes 3 as by many experiments differing ways made is 
very plainly vifible. 

This plainly gives the caufe why knots and Tophus's 
do ask were grow to the Wick of the Lamp like fo many 
Mufhrooms on a rotten Tree, which as foon "as they are 
removed out of the middle and dead part of the flame 
are immediately confirmed by, and diffclved into the 

Air, and fhine like a coal of fire, as being indeed nothing 
ehe. 

Hence we may give a plain Reafbn why upon applying 
any cool Superficies very low into the flame of a Lamp, 
there is immediately conden(ed upon it a great quantity 
of foot, namely, that the middle parts of the Cone of 
flame, being nothing but a great number of oyly (teams 
afcending, are not fired nor confomed by the Air, till they 
can come to be wrought upon by ■•the.-free and unfatiated 
Air. Now if the Aiivbe (b intercepted that it cannot 
come at them, and the (teams be cooled by the plates 
coldnefs that the Air is not able to prey upon ordiflblve 
them for want of a preparatory heat (ufficient, they muff 
i emaknn the form of burnt Oyl, or Lamp-black. 

I have been, fbmew hat the longer and more particular 

in 



(9) 
in thisdefcription and explanation of my Theory of the 
flame of a Lamp or Candle, that fo the Reader under- 
ftending the nature and caufes thereof the more fully and 
piainly, he may the eafier difcover the inconveniences 
that may occur in the burning, heating, Ihining, durati- 
on, &c thereof and the fooner and more readily and 
fcientificallyfind a cure and prevention of thofe inconve- 
niences, which he that is ignorant of can but hood- 
winked grope after and at bed can but hope poffibly 
after long puzhng himfelf in vain attempts and blind 
trials, nothing to the purpofe, he may at length (tumble 
upon that which had he been inlightned by the true The- 
ory,he would have readily gone to at the firft dance 

I could have further expatiated into the contem- 
plation of this moft admirable Phenomenon of flame 
producing heat and light, the two moft fpirituous 
and. moft potent Agents in Nature, and the ways of 
Intending and Diminifhing them, and the ufes that may 
be made of them, but that it is not my prefent defign 
to annex a difcourfe on thole fubjefts, which doth 
more properly belong to another Lefture I (hall fhort- 
ly pubhfh, I (hall therefore at prefent proceed only 
to (hew fome Mechanical contrivances for counter- 
poifing Liquors in Veflels, fo as to keep them runhing 
or fupplymg a ftream always with equal fwiftnefs,what- - 
ever quantity there be of the faid Fluid 3 which as they 
are very convenient for peifefting Lamps for divers ufes, 
which they could not otherwife perform, fo in Hydrau- 
hck^ they are of moft admirable beneht for divers 
effedrs hardly to be performed without them, as Khali 
hereafter manifeft. But firft, I will explain fome few 
ways by which more conveniences may be obtained and 
more inconveniences prevented in the ufe of Lamp's for 
Chymical, Mechanical, and Philofophical ufes than by 
this way of Cardan, or any other I have met with : For 
this I look upon as one of the Tools to be made ufe of 
in the Work-houfe or Elaboratory of Nature, without 
a good Apparatus of which, be the Workman otherwife 



nevei 



(10) 

never fo well aecomplifhed, he will never be able to pro- 
duce any very considerable effect .5 and with them, even 
a Bungler other wife, will, if well furnilhed, do won- 
ders to fuch as know not the means by which they are 
done. 

It may pofEbly feem very ftrange to fome to hear,that 
by the flame of a Lamp Plants may be made to grow, 
bear Leaves, blow Flowers, ripen Seeds % that the Eggs 
of Fowls and Infects may be hatched, and brought to 
life and perfection } that Metals, even the hardeft, Glafs, 
Stones, &c. may be almoit in a moment melted, foft- 
ned, liquified, hardned, &c. that thoufands of fepara- 
tionsof conjoyned and naturally United bodies may be 
efl e&ed, and they refer ved difiinct 5 and as many other 
bodies, naturally diftinct, and very differing, may be 
united and compounded into Homogeneous mixtures, 
fome fcarce feparable afterwards 3 that Glafs may be 
fliaped and moulded like Wax $ that almoft all the fen- 
fible qualities of bodies may be increafed, diminifhed, 
annihilated, and created 5 and fome alfb of the qualities 
infenfible ( otherwife than by the effects 3 ) and yet even 
theft, and many more, may be effected by this Tool or 
Inftrument, if rightly uftd, as I could manifeft if I had 
now time. But I fhall not here any further expatiate on 
it, pofGbly I may hereafter but at prefent I fhall only 
proceed to the defcription of one fort of thofe In- 
flruments which ferve to fupply the Oyl or Pabulum of 
a Lamp conveniently by any degrees, and in what quan- 
tity is dented. This fort doth depend upon fome con- 
trivance of Counterpoifes for the Liquor in the Re- 
ceptacle that is to feed theLamp, and may be made life of 
in Hydralicks as well as Lamps to feed and continue any 
running ftream any time defired. 

Thefe Counterpoifes then of Fluids might be made to 
feed the flame of a Lamp equally for any time affigned, 
and confequently would make a kind of Perpetual Lamp, 
but the Pabulum itfelf will be fome ways or other unapt 
for fuch an effect 3 , as Oyl hatha foulnefs whereby the 

Wick • 



00 

Wickischoakedorftopped, fo as that it will no longer 
afcendinit$ Spirit of Wine will in length of time eva- 
porate andlofemuchof its nature 5 and other Oyls have 
their feveral defe&s which make them uncapable of con- 
tinuing the flame very long. But there are none of thefe 
that I have met with but may be in great meafure avoided 
by the help of fome Chymical or Mechanical contri- 
vances, fome inftances whereof I ihall hereafter give, 
which the Theory of Fire and Flame doth readily 

hint. 

The firft way then I (hall nowdefcribe is by a round 
Box, the inward Cavity of which is divided by a Dia- 
phragm into two equal parts, and fitted with a proper 
Counterpoife, the Axis of whofe motion lieth Horizon- 
tally. The contrivance of which will be more plainly 
underftood by the Delineation thereof in the firft place, 
where the fecond Figure reprefents the whole Inftrument, 
with its Globe, Frame, Pedeftal, Socket, and lighted 

Lamp. 

A reprefents the Pedeftal or foot upon which the Tn- 
ftrumentftands,which may be made of Silver, Brafs,Wood, 
or the like. B C D E F, the Frame faftned to the Pedeftal, 
andftiapedintheform of a Snake, perforated at BandD 
to receive the Pivots or Gudgeons of the Lamp G H, and 
hollow from E to F to ferve to convey the Oyl or Spirit 
of Wine from the end of the hollow Gudgeon H to the 
Wick I, to feed the Flame Kj the hole at E to receive 
the end of the hollow Gudgeon } H is made a little ta- 
pering, and the end of the Gudgeon H is .ground fit into 
it, foas toturneafily, and yet fo true, as not to let any 
Oyl there leak out, the faid Gudgeon being kept clofe 
home by the fpringing of the Arm B 3 the Superficies of 
the Oyl or Spirit for the Pabulum is always kept by the 
motion of the faid Globe upon its Axis G H, exa&ly in the 
LineLM, untillitbe allconfumed, which how it is done^ 
will be better conceived by {hewing the contrivance of 
theinfide of the aforefaid Globe, how the fame is divi- 
ded, how filled, and how counter poifed. 

C 2 Suppofe 



(12) 

Suppofe then the aforefaid Globe cut in funder tor 
the. middle Line or Circle N O, and difcovering the In- 
fide or Cavity thereof to be reprefented in the hi it Fi- 
gu re, where P A H R Z P reprefents the aforefaid Circle, 
or half (hell of the Globe , O reprefents the middle of 
the hbllow Gudgeon H, which is the Pole or Axis about 
which the faid Globe doth move. H O Z reprefents the 
Horizontal Line or Plain paffing through the aforefaid 
Axis 5 P R the Perpendicular to that Plain, Let H Z then 
represent a Diaphragm or Partition of the fame material 
with the Globe, by which the Concavity thereof is divi- 
ded into an upper Hemifphere H P ZO H, and into an 
under Hemifphere HRZOH. Let the under Hemi-., 
fphere be rilled with Oyl, Spirit of Wine,^. or the like 
fit material for a Lamp to burn 5 and let the upper part 
be filled with fome material of half the weight of the 
Oyl, Spirit, or other material, or becaufe that will be 
fomewhat difficult to do, let there be a counterpoife of 
Lead or other ponderous matter fixed fbmewhere in the 
Line PO, fo that the {aid upper Hemifphere (hall have 
half the gravity of the under Hemifphere upon the 
Center of motion O. I lay, whatever quantity of the 
Fluid Pabulum is in the Cavity of the (aid ., under He- 
mifphere, the Superficies thereoflhallalways.be in the 
Horizontal Line or Plain O Z, the counterpoised upper 
Hemifphere keeping it always up to that height. For 
inftance, fuppofing the faid Hemifphere full, there is no 
doubt but that the under Hemifphere being double the 
weight of the upper moft will be lowermoft, and that 
Horizontal Line will lie Horizontally, fince it is evident, 
that the Center of gravity of the whole will be below 
the Center of motion O, and fomewhere in the Line 
O R, which is Perpendicular to the aforefaid Plain. Next, 
fuppofe (b much of the aforefaid Liquid Pabulum con-, 
fumed as to leave enough only, to fill the fpace 
G O Z B RC, and the Diaphragm be moved from its Ho- - 
rizontal Pofition HZ, and placed in the Oblique Pofi- 
tion COD. I fay, the faid upper Hemifphere 

CHAPDOC 



(i3) 
C H A P D O C (hall exactly counterpoife the faid under 
Hemifphere CRBZDO C, fo as the Superficies of Li- 
quor (hall be in the Horizontal Plain OZ. Make AP 
equal to P D, and draw the Line A O B through the 
Center O, it is manifeft then that the Wedge COR of 
the Liquor doth counterpoife the Wedge ROBon the 
other fide the Perpendicular, and that the Wedge POD 
of the upper Hemifphere doth counterpoife the Wedge 
POA on the other fide of the Perpendicular, fo that 
neither of thefe have any prepollency to move the Globe 
out of this Poflure. Next, it is plain that the Wedge 
B O Z of the Liquor will be counterpoifed by the Wedge 
A O C, which is double the bignefs of BO Z, and con* 
fetjuently of equal weight, the parts of the upper He- 
mifphere being put of half the gravity or weight of the 
under Hemifphere. 

Next, fuppofe half the Oyl be confumed, and there be 
only left enough to fill the quadrantal Wedge ZO R, 
I fay, the Superficies thereof fhall be in the Horizontal 
Line O Z 5 for fince the upper Hemifphere is half the 
Weight of the under, the two quadrantal Wedges P O H 
and H OR. muft neceffarily counterpoife the quadrantal 
Wedge ROZ of the Oyl. 

Thirdly, Suppofe that more than half the faid Oyl or 
liquid Pabukntbt confumed, and that there be only left 
enough to fill the Wedge B OZ, I fay, the counterpoi- 
fing upper Hemifphere now made the under, and placed 
in the Pofition AHCRBOA fhall exactly counterpoife 
the faid Wedge of Liquor, fo as that the Superficies 
thereof fhall be in the Line O Z> for the Wedge R O B 
of the aforefaid upper Hemifphere doth counterpoife 
the Wedge G O R on the other fide of- the Perpendicu- 
lar, and the double Wedge A O H and HOC will coun- 
terpoife the Wedge BO Z. 

Nor can the Superficies of the Liquor be any whit 
higher or lower than the Line OZ, for if it beany whit 
higher as at EF, the Liquor muft neceffarily overpoife 
the aforefaid Wedge A O C, by all the weight of the 



(14) 
Liquor contained in FGOZF. And if it be any 
whit lower as at IK, the Wedge KIB muft be too 
light for the counterpoising Wedge A O C by the 
weight of the Liquor contained in the (pace 
ZOTKZ, fince I juft now (hewed that AOC did 
juft counterpoise Z O B, which was the thing to be 
proved. 

Now though in this Inftance I have chofen to explicate 
I have made choice of a Globe;, yet that form is not ne- 
ceffary, but it may be made of any Figure whatfbever 
that is turned upon an Axis or Poles, fo as wherefbever 
the (aid Figure be cut by a Plain to which the Axis is Per- 
pendicular, the Superficies of the faid Figure fhall de- 
fcribe a Circle, the Center whereof is in the faid Axis, 
whether the (aid Figure be a Cylinder Cone, or any 
other Conoeidical, mixt, or otherwise, regular, or irre- 
gular figure. Such as the Figures ABC D E F G, which 
reprefent the Section of the laid Veflel through the 
Axis. 

The fecond way for the poyfing the Liquor, and 
keeping the Superficies thereof always to an equal height, 
is this : 

Make a Concave Receptacle for the Oyl or Liquor of 
a Hemifphencal, Semicylindrical, Semiconical, or of any 
other half-round hollo w Figure, where the turned Figure 
is cut in two parts per Axin^ and whereof the Axis is 
placed Horizontal, and the plain Se&ion per Axin like- 
wile Horizontally ,fo as it may be filled with any Liquor 
up to that Plain 5 and that the Liquor may not be apt to 
dafh, be fhaken, or filter over, it will be convenient to 
extend the brims of that Receptacle fomewhat above 
the half-Round, that there may be about half or three 
quarters of an Inch of fpace above the Superficies of the 
Oyl vacant or empty. And that upon whatever Plain the 
foot ftand, the Plain per Axin may ftand Horizontal, it 
will 'be good to fufpend the Receptacle in the fame man- 
ner as a Sea-mans Compafs is lliipended, within a frame : 

Fix 



C 15 ) 
Fix this Receptacle, or the Frame that h to keep the 
Receptacle, Horizontal upon a convenient Pedeftal$ 
and fit within the Hollow or Concavity of the Recepta- 
cle a half-round folid poke, turned of the fame form 
with the hollow of the Receptacle, and cut exa&ly 
through the Axis in two equal parts. Let this folid 
poife be made exaftly half the weight of the Liquor that 
is. to be poifed, and fit to it two Pivots or Pins at each 
end of the Axis, which may be exa&ly in the Poles of 
the half-Round, and fit to thofe Pins make two holes in 
the Centers of the Ends of the Concave Receptacle, in 
which the Pins may freely move, and fuffer the half- 
Round poife to move round within the hollow of the 
Receptacle, according as the quantity of the Oyl or Li- 
quor is increafed or diminifhed. Fit to this Receptacle 
a neck and focket fit for the Wick and flame of the 
Lamp, and the fame operation will be performed by this 
as by the firft contrivance $ to wit,the Oyl will be kept al- 
ways to the fame height in the Receptacle. 

This will be eafier underftood by explaining a De- 
fignation thereof which is fhadowed forth in the fourth 
Figure : Where 

. AAA reprefents a PedeftaJ, which maybe made with 
three claws or toes tomakeitftand the Headier and even- 
ner upon any Plain or Table. 

BB reprefent one of the Semicircular Arms that are 
fix'd to the top of the Pedeftal, this hath two holes in it 
at the ends or extremities, as at C is one, the other hole 
being in the other arm which goes behind the Globe, 
and therefore cannot be feen, is fuppofed to be Diametri- 
cally oppofite to this at C. Thefe two holes are the Cen- 
ter holes in which two (mall Pins or Centers, faftned into 
two oppofite points of the Hoop or Frame are made fit 
to move, by which means the faid Hoop is prefer ved to 
an horizontal Pofition, 

D D is this Hoop or Frame, which is made toine: 
pafs the Veffel or Receptacle of the Oyl, and is fbaped 
nxaftly like it. This is made ftrong enough of 



(16) 

Iron, Silver, or other material to bear the Receptacle, 
Poife and Oyl without bending, and hath, as I faid be- 
fore, two Pins or Gudgeons at C, and oppofite to it Di- 
ametrically, or Semicircularly,.upon which the faid 
Hoop always hangeth Horizontally* It hach alfo oh each 
fide in the middle between the aforeftid Pivots, two 
Centers as at F and E to receive the ends of the Axis of 
the Receptacleappearing at F andE, by which the faid 
Receptacle is always free to hang plumb or in its Perpen- 
dicularity, fo as that the upper edge thereof at F F will al- 
ways lie Horizontally. 

One of thefe Pivots, namely, that on the Right hand 
is the Pipetoconvey theOylto theSocket oftheLampI, 
in which is fitted a Wick of Cotton to ferve for the 
flame, KGG reprefents the Veflel or Receptacle of Oyl, 
which is here defcribed Hemifpherical, that being the 
moft capacious uniform Figure, but may be of any other 
qualified as thofe I mentioned in the firft contrivance! 
The Brims of this are extended fomevvhat higher than a 
Semicircle, namely, to F F, to keep the Oyl from flafhing 
or filtring over. This is always kept full with Oyl or 
other Liquor to the Horizontal prick 'dLine L L, which 
pafleth through the Center or Axis of its Cavity by the 
Counterpoife moved on the Center C. 

H H H reprefents that Counterpoife which is made ex- 
actly half the weightof the Oyl or Liquor, and the Cen- 
ter of gravity of it muftbefomewherein the Line M M 5 
and it ought to befitted as -exactly into the hollow of the 
Receptacle as it is poffible, that there maybe left aslittle 
fpace as may be between its convex fides and the Con- 
cave of the Receptacle, but yet fo much mull: be left 
that it may move very freely upon its Center C a whole 
Semicircle. This done, and the Receptacle being fil- 
led with Oyl, the fame effect will follow as in the firft 
contrivance, and the Demonftration of it being much 
the fame, Khali not now fpend time to explain it. But 
rather proceed to the defcription of a third way of 
keeping the Liquor counterpoifed to the fame level. 

The 



The third way then is : 

Take any round Veffel, whofe Concavity and Con- 
vexity is turned upon an Axis, and fufpend that Veffel 
upon two fmall Pivots Cbut yet big enough to bear the 
faid Veffel filled with Oyl, &c.) faftned in the Poles of 
that Axis 3 and leave or cut open a fixth part more or lefs 
as you pleafe of the fide thereof, that thereby any thing 
may be put into or taken out of the Cavity of the Veffel 3 
then poife the Veffel exa&ly on thofe Centers, that no 
fide be heavier than the other i then fit into it a float of 
Brafs, Silver, Tin, Lead, &c. Convex on the under fide, 
foas juft to fill to the Cavity of the Veffel. And on the 
upper fide, Plain, or Convex, or any other convenient 
Figure, it matters not much. Make this float as heavy as 
you can at the bottom, and as light as may be at the top, 
but yet of fuch weight as may well float upon the top of 
the Oyl, &c. Let one end of this be faftned by a wire or 
firing, fo as that end thereof may always touch that 
point of the Concave of the Veffel to which it is tied, 
and that the reft thereof may turn and follow the fink- 
ing of the Oyl 3 and through the end of it, near the place 
where it is faftned, let a Pipe go through it to receive the 
Wick, which Pipe hath no communication with the Ca- 
vity of the hollow float. This done, fill the Veffel as full 
as convenient with Oyl, and light the Wick, and you 
ffiall find that as the fire confumeth the Oyl, the Veflel; 
will turn upon its Poles and keep the Superficies of the 
Oyl always at the fame diftance from the flame that it was; 
put at at firft till the whole be confumed. 

This will be made more conceivable by a figure and 
explanation thereof; which therefore take as follows 
in the fifth figure. 

A C B B reprefents a hollow Veflel, the Cavity where- 
of is very exactly turned upon an Axis whofe Poles are in 
P, the fpace between A and B in the fide thereof is left 
open into the Cavity of it. This Veffel is fufpended 

E> ■ upon 



cm 

upon its Poles at P, fo as to be free to move round upon 
them, and exaclly poifed as no one fide thereof be hea- 
vier than another. To the hollow of this VelTel is fitted 
a float D of Brafs, Latton, Silver, Lead,e£r. ■ whofe under- - 
fide is made of a Convexity juft fit for the Concavity of 
the Veffel, as may be feenat KDI,andtheupperftraight 
or Plain. Let this float be made fomewhat lighter than 
the Oyl or Liquor on which it is to fwim, fb that a part 
thereof may float above the Superficies thereof Let one 
end thereof E be faftned to the fide of the VeiTel a little 
below the Brim B 5 through the end of this float is put a 
Pipe and Wick h, for the flame i, then pouring in Oyl 
by the open fide A QB, fill the fame till it carry the float 
up to touch the hollow of the VeiTel 3 then light the 
Wick, and you will find that the Lamp will confume the 
Oyl, and this contrivance will continually fupply it till 
the whole be confumed, and the Poife be moved to 
touch the Concave of the aforefaid VeiTel 5 for when the 
VelTel is filled up to f g, the float D will touch at O and 
E, and the Cavity above f g being empty, the Veflel will 
be as is defcribed in the Figure, the open part A B being 
upwards. And as the flame coniumeth the Oyl, the fide 
of the VeiTel B will defcend downward towards B 1 3 
andfobyB 1, B 2, Bg, to B 4, where the whole quanti- 
ty of Oyl will be confumed, and the bottom of the float 
will touch the hollow fide of the Veflel $ in all which 
gradual wafting of the Oyl the Superficies thereof will lie 
atthe fame diftance below the upper fide of the .float D 
that it had atfirft, and consequently at the fame diftance 
from the bottom of the flame. The reafon of all which 
will be very eafieto beunderftood by any one thatfhall 
ferkmfly on this Delineation confider that the float D muft 
necefiitate the Veflel A CB to move on its Axis B ac- 
cording as its Oyl wafts,becaufe one end thereof E being 
faftned to the brim of the Veffel B, the other end O be- 
ing loofe will as the Oyl wafts defcend towards N, whence 
the end E muft hang heavier on the brim B, and confe- 
quentlv muft move it down towards B till the upper 

fide , 



0-9) 
fide fg of the float be. reduced to a Parallelifin with the 
Superficies of the remaining Oyl, and the end E have no 
gravitation on the brim B, which motion will be continu- 
ed as the Oy! wafts, and the brim B will be moved down- 
wards by the points B i, B 2, B 5 , to B 4. I (hall not 
therefore fpend any more time in the Geometrical demon- 
ftration thereof, but proceed to explain a fourth way by 
which the Flame and Superficies of the Oyl keep always 
at the diftance they were firft put at. 
• 
The Fourth way then is, the making the Socket of the 
Wick to fwim upon the top of the Oyl, fo that the 
Socket may fink as well as the Oyl, by reafon it is fuftai- 
nedbythat, and by that only. The Veffel or Receptacle 
is generally made of Clafs, and it is beft of a Hemifphe- 
rical Figure, the light cafting it felf through the body of 
the Oyl as well as of the Glafs. This is fo plain and obvi- 
ous, andfo commonly ufed and pra&ifed, that I need not 
ipend more time in the explanation ov demonftration 
thereof, but proceed to defcribe a Fifth way. 

The Fifth way then is much upon the fame principle 
with the Fourth, but avoids feveral inconveniences to 
which that is fubjeft: For whereas the Flame in the 
Fourth is necefEtated to be within the capacity or the 
Receptacle in this Fifth, it may be at any diftance, and 
fo is made much more convenient to be come at, and to 
be dreffed and trimmed. Take then a Vetfel of Ghfs Cy- 
lindrical is beft,as a Clafs Bottle,and fit to it a Siphon lone 
enough to draw the Oyl from the bottom of the faid Ve(~ 
fd, make the one end of this Siphon extend at what di- 
ftance you think convenient for the placing the flame of 
the Lamp, and fo order it that it may always draw from 
the Receptacle by its arms to feed the flame, which it 
will do if the end of the Siphon be made where the 
Socket of the Lamp is placed to return or bend upwards 
again. So that the Plain of the upper Superficies of the 
Oyl may cut that end of the Siphon where the flame is 

D 2 between 



between the top of the mouth of it next the Socket and 
the return thereof upwards $ then by a counterpoife fo 
fufpend this Siphon that it may follow the Oyl as it wafts, 
and fit into the return of the Siphon a Socket and Wick 
for the flame to be continued, A contrivance foirie wha t 
of this kind you have in divers Authors, and therefore I 
iliall fpend iefs time in the defcription thereof. Let 
AAA A in the Sixth Figure then reprefent aJarge Cylin- 
drical Viol of Glafs through the mouth B of which the 
Cavity thereof may be filled with Oyl, and alfo the end D 
and float C of a convenient Siphon may be put in.. This 
Siphon DD DPG-muft be made long enough that the 
float C may reach the bottom of the Veffel. when the 
Oyl is fpent, and the other end thereof muft be fo curved 
that the kneeof the Siphon P may be below the Super- - 
ficies of the Oyl E F, and yet thatthe Socket H made for 
holding the Wick fbr the flamel may be fbmewhat above 
it, this Siphon DDD P O with its Socket and float 
fhould befo counterpoifed with a weight M, hung over 
a Pulley K, bya ftringL, thatthe float may not fink deep 
into the Surface of the Liquor,, but fwim as it were at 
the top. This done, if the Wick I be lighted, the Surface 
of the Oyl will be kept always at theXam&diftance below 
the flame that it was firft put at. 

In the firft, third, fourth, and fifth ways the flame of 
theLampdeibends equal (paces with the Superficies of 
the Oylinthe Veffel, and therefore though for- fome ufes 
it be very convenient, as in annealings^ where things are 
to be cooled by degrees,, yet for many other it is not$ 
Efpecially in Lamp Furnaces, where the fame heat is to be 
continued^ and in fome cafes gradually increafed.i For 
fuch cafes therefore the firft and fecond ways will be 
very convenient. In fome other cafes thefixth andievcnth 
ways,- which do much the fame thing. 

The fixth way then is this : Through an arm or Siphon 
( like the Branch of a Lamp hung againft a Wall ) fixed 
» any convenient place, the Oyl from the Receptacle is 
7 ' continually, . 



continually and equally fupplied to the flame of the 
Lamp by the railing of the Receptacle as faft as he Oyl 
wafts, fo asto keep the Superficies of the Oyl alway m 
the fame Horizontal Plain. The Receptacle is ; raifed by a 
Counterpoife hung upon a Fufey, which Fufey is a part 
of an Archimedean Spiral. 

Let C C then in the feventh Figure reprefent the Recep- 
tacle for the Oyl, being a Cylindrical or Pnfmatical 
VefleL of what; Bignefs or Length you pleafe; to this 
by two Ears at L L faften two Lines or Ropes K K, the 
ends of both which are faftned to the Wheel or Pulley G, 
though one of them do run over the Pulley F. Fit into 
this Receptacle is made a Cylindrical or Pnfmatical 
Plus A A, which is fixed in Tome- convenient place fo as 
not to rife or fink, and through the middle thereof pafi 
feth a Siphon BBB, the one end whereof extended like 
the branch of a Candle or Lamp fuftains the Socket D 
for the Flame E, which is fed with Oyl through the Si- 
phon B B B by the rifing Receptacle C C. 

To the fide of the Pulley G is faftned a- Fufey H, 
made with very great care of one Revolution of an 
A chimSean Spiral, not beginning from the Center, but 
from fome convenient d.ftance from it, where the 
weight I hanging, may juft counterpoife the Receptacle 
Cc! when quite empty of Oyk the other hanging coun, 
terpoife(Tangent to the largeft part of this^Sp. a ) mutt 
befb fardiftant from the Center of the Wheel G that 
the fame weight I may juft counterpoife the faid^Re- 
ctptade fiStop-full^ oi Oyl, and the Fuley muft be 
filed true to a Spiral, drawn with great care of one 
Revolution between thofe two points. ^ I fay here of 
ond Revolution, becaufe I have fuppofed the Wneel 
ofpulley G big enough, by one Revolution of it to 
d aw up the Receptacl! the whole (pace it is to be rai- 
fedT forif the laid Pulley be fofmalkas to. require two, 
three four, or more Revolutions, then muft thej.ece 
of the Sphal between thofe points be .drawn of two 
lee, four^ormore Revolutions proportionably, wh ch 



being very Artificially and Mechanically performed, the 
Receptacle C C will be railed by the fame Degrees by 
which the Oyl is confumed at E, and the upper Super- 
ficies thereof (hall always be in the fame Horizontal 
Line MM. The Geometrical and Mechanical Reafbn 
of which being fo very plain, I hope I (hall not need to 
fpendany more time in the explication thereof than only 
to fay, that by means of the Archimedean Spiral-Fufey 
the Power of the weight I upon the Pulley G decreafeth 
in the fame proportion as the weight of the Oyl in the 
Receptacle C C is diminifhed by its confumption. 

The feventh way then is] by a Cylindrical or Prifma- 
tical Plug fitted into a Cylindrical or Prilmatical Re- 
ceptacle, and let down into it by a Counterpoife, hung 
upon a Spiral Fufey, the Oyl is fo raifed in that Recepta- 
cle as always to ftand Brimful], or to the fame Horizon- 
tal height till the whole Oyl be confumed. 

The contrivance of this way will be very eafily under- 
ftood by any one that fhall perufe the Delineation in the 
eighth Figure, and examine it by this following defcri- 
ption. 

Let A A in the eighth Figure then reprefent a Cylin- 
drical or Prifmatical Receptacle, (landing fixt upon a 
Table or Pedeftal, from the fide of which iffues a hol- 
low Arm or Branch BB, bearing the Socket for the 
WickC, where the flame Discontinued. Into the Ca- 
vity of this Receptacle is fitted a Cylindrical or Prifma- 
tical Plug EE, big enough to fill the whole capacity 
thereof, and yet not fo elofe but that it may freely flip up 
and down the Cavity of the laid Receptacle without 
linking. Let thisPlugbe made considerably heavier than 
the Oyl of the Receptacle^ that is, let the Counterpoife 
L, hanging upon the little Wheel M juft reduce its gra- 
vity to be equal to that of the Oyl } then let the point I, 
where the Perpendicular toucheth the Spiral, be To far 
removed from the Center of the Wheel H, that the coun- 
terpoife 



terpoife h may juft take oftits whole gravity, and fuffer 
it to have no degree of gravity or preflure downwards. 
Then draw the Spiral no p according to the direction! 
' gave in the former way, and the effed will be produced. 
The Geometrical and Mechanical Demonftration of 
which is very plain to any one that {hall confider,that,As 
the Plug EE by finking into the Receptacle A A fo far 
as to raife the Oyl to the Horizontal Superficies M M 
will lofe its gravity by the fame Degrees by which it 
finketh into the Receptacle, and that is alway propor- 
tionable to thediminiihing of the Oyl in the Receptacle 
by the flame : So the weight L will lofe its power upon 
the Wheel H,by the fame degrees by which the Plug de- 
fcendeth, by reafon the Line by which it is fufpended 
becomes a Tangent to a proportionately fhorter Radius 
of the Spiral, of the Rays of the Spiral. 

I know indeed that both in this and the former Fufey 
there lies an objection againft the true form of the Spiral, 
becaufe the Line K K of the weight L doth not touch the 
Spiral in a point level with the Center,, but in one fome- 
What above it, and in this latter fomewhat beneath it 3 
but though that be a feeming material one, yet as to 
practice it fignihes very little. For firft, it will not be 
difficult to prove that this may be Mechanically drawn 
true enough,that there ihall be no fenfible error,and if the 
errorbe not fenfible,it is no error in praftical Mechanicks. 
Next, were it the true Spiral, yet it would not be more 
Geometrically Delineated than this which is here requi- 
red, and at^beft it would prove but a Mechanical ap- 
proach, which isiiifficient for the effect to be produced 
by it. 

Thefe two laft contrivances do keep the flame of the 
Lamp always in the fame place, and of the fame ftrength 
and fulnefs. But the fucceeding ways, though they 
maintain the flame in the fame degree of ftrength and 
nourifhment, yet by their motion upwards they may be 
made to increaie, and intend the heat produced by them 
in the bodies pofited above them, which is of great 

ufe 



life in many Chymical and Philofophical Experi- 
ments. 

The eighth way then is this : Make a Cylindrical or 
Prifmatical Receptacle for the Oyl exa&ly like the for- 
mer, with its Arm, Socket, Wick, &c. and fit into it a 
Cylindrical or. Prifmatical Plug, as in the former, that 
may be able to fill the Cud Receptacle. Fix this Plug faft 
into fome Wall or Standard, fo that it (hall notbe able to 
ftir 5 Then by the help of two Lines faftned to a Coun- 
terpoifeat one end, and the other to the Ears of the Re- 
ceptacle, fo counterpoife the faid Receptacle that it (hall 
have no weight or gravity downwards, but hang in a 
perfect equilibrium 5 I fay, whatever quantity of Oyl 
there be in the (aid Veflel, the Superficies thereof {ball 
always be in the Plain which is equal to the top of the 
Oyl when the Veflel is filled as high as isdefired, which 
will very plainly appear to any one that (hall examine 
and confider well this following defcription, and com- 
pare it with the Delineation of the Inftrument in the 
ninth Figure, where A A reprefents a Receptacle for the 
Oyl of any convenient capacity, made Cylindrical or 
Prifmatical, to which is faftned a hollow Neck or Arm 
B B for bearing the Socket C, to which through its Ca- 
vity ( being made hollow ) is conveyed the Oyl or Pa- 
bulum for the continuance of the Flame D f, into this Re- 
ceptacle fit a Cylindrical orPriim&iicalPlug, foasit may 
pretty equally fill the faid Cavity of the Receptacle, 
yet notfb as any ways to hinder the Aiding on upon it of 
the Receptacle, Let this Ph.- then-be fixt by the top in 
any convenient place Perpendicularly,, and fetting the 
Receptacle underneath it, Counterpoise 'the fame when 
filled up with Oyl by a Counterpoife I, which is faftned 
to the two firings FFFF, by which the Receptacle is 
to hang, which two firings for their more eafie Aiding to 
and fro move upon the two Pulleys or Truckles G G, 
that are fixed to the (ame frame to which the Plug E E 
is fixed} which being fo adjufted, as faft as the flame D 
confumeth the Oyl out of the Receptacle A A, the 

Counter- 



€*0 

Counterpoife I raifeth the faid Receptacle on upon the 
Plug fo far till the top of theOyl be equal to the height 
it was at firft counterpoifed at, to which height it always 
keeps it till the whole be confumed. 

Thislaft way of poifing the Liquor or Oyl doth make 
the Superficies thereof run higher and higher as the 
quantity thereof is more and more confumed, which 
for divers Expedients in Mechanicks,NaturaI Philofophy, 
and Chymiftry is of excellent ufe, as I may hereafter 
have opportunity to manifeft upon many occafions 
wherel (hall make ufe of them; and it would be,I fear,too 
tedious to the Reader to have them here enumerated' 

Buttecaufe it may not poffibty be ungrateful to him 
to have fome ufes of this Principle here hinted, I fhall 
now fpecifie a few, and hereafter add many more, toge- 
ther with a great number of other Poifes for Liquors 
which ferve for very differing effefts in their kinds, 
not left considerable, but rather fomewhat more ftrange, 
as being yet farther removed from the common praftices 
and difcourfes of Hydraulicks. 

The firft ufe then that I (hall mention of this Liquor- 
poife (hall be in Hydraulicks, viz. to make a Ciftern of 
whatever bignefs and depth is required to deliver all 
its water at the top, or fo near unto it as it (hall be de- 
fired : By which means nothing of theDefcent of the 
water falling into the Ciftern is loft, but without any la- 
bour or trouble the whole quantity of water that is de- 
livered at the top into the Ciftern is re-delivered again 
out of the Ciftern at the top. This may be done by the 
firft, fecond, and feventh ways of poifing Liquors 5 this, 
that, or the other, of which may be more convenient 
to this, that, or another effeft or operation to be per- 
formed by it, which muft be chofen and applied with 
judgment, according to the occafion, and the circum- 
ftances of it. Every of the three, though they all agree 
together in the producing the effed of keeping the Su- 

E perficies 



perficiesof the water to the fame Level, and there de- 
livering it, have yet each of them their feveral proprie- 
ties, which maketh fome one of the three more proper 
and adapted to onedefign than either of the other two, 
and each of the other two in fbme other effeds and ap- 
plications may be much more ufefully applied than the 
firft. By this means the whole depth of the Ciftern is 
gained, and all that water that was ufed to be delivered 
at the bottom is now delivered at the top, and confe- 
quently gains the advantage of the Perpendicular height 
of the Ciftern to be imploy ed, for any ufe, for turning an 
Automaton, or conveying the Stream farther, or to a 
higher level. 

A tecond effeft performable bythefe Poifes maybe 
for delivering any quantity of water with an equal de- 
gree of fwiftnefs, io as to continue an equal fupply of 
water till the whole Ciftern or Receptacle be emptied, 
the fpending of the water in the Ciftern not at all 
abating the ftream without, the Counterpoife always 
keeping the Ciftern full, and maintaining the current till 
the laft. This may be ufeful for lawing or grinding 
ftones by an Engine } for gauging of Glafs Tools, or 
grinding glafles by an Automaton, in all which cafes 
there is need of a conftant and equal fupply of water 
andfand, asalfo for wafhingand Fulling of Cloth } it 
mayalfoierve for various forts of Clepfydras, or mea- 
suring the quantity of time by the quantity of the cur- 
rent of water, as I fhall by and by fhew. And thirdly,, 
for maintaining any flow and conftant motion, as that 
of a Jack, or Clock, an Engine for continually ftirring 
of a liquid body, or fhaking, tumblings and turning of 
dry Solids and powders, of which fort there are a 
great number of ufes in Chymiftry for the operations of 
Digeftion, Calcination, Pounding, Grinding,Trituration r 
Searcing, and the like 5 which operations being certainly 9> 
evenly, and conftantly performed by an Engine fupplied 
by fuch a ftxeam of water will far exceed the fame kind 



C*?3 
of work done by the hands of men, efpecially in fuch 
operations where the Labour and Diligence is to la ft 
divers days and nights together without any intermiffion, 
whichare Requisites not at all ftrange to Chymiftry, and' 
which will weary the diligence of thebeft Laborant and 
his Attendants. 

^ A third efTe<3: performable by thefe Poifes is the ma- 
king a perpetual and conftant ftream in imitation of that 
of a natural Spring or Fountain in the Earth. This may 
be done if the Ciftern be once in twenty four hours re- 
cruted and fupplied with a new accefs of water from 
fome Pipes, which is ufual enough here in London, and 
elfewhere, where there are Waterworks and Convey- 
ances of water. For as the wafting of the water in the 
Cittern does no ways abate or diminifh the dream of the 
water from the Ciftern, fo the new accefs of other wa- 
ter for a fupply to refill the Ciftern does not at all accele- 
rate it, but the ftream remains equal. And hence,, con- 
fequently conftant, and, as it were, perpetual. 

A fourth efTecl: is, the delivering any quantity of wa- 
ter to any degree of fwiftnefs, and the whole quantity 
of the water by the fame degree. This is performed by 
tapping the Ciftern at any part of the depth thereof, for 
according as the Veilel is tapp'd lower under the 'sur- 
face, fo will the motion of the water be fwifter 3 and 
here the depths muft be in a duplicate proportion to the 
Velocity defired : Asfor inftance, the Ciftern being tap^. 
ped with a hole of a quarter of an Inch bore, at the 
depth of an Inch below the Surface, is found' to de- 
liver a certain quantity of water in a minute 3 if it be 
defired that through a Tap of the fame bore there fhould 
be delivered twice that quantity, the Ciftern muft be 
tappUatfour Inches deep* and if thrice that quantity in 
the fame time, it muft be tapp'd at nine Inches deep 3 and 
fo forwards, as is already demonftrated by Merfewrur, 
and other Authors. For fince the preffure of Fluids 
upon the parts thereof increafe, in the fame proportion 

E 2 with 



(=8) 
with the depth beloW the Surface. And fince the forces 
requifite to accelerate motions muft always be in du- 
plicate proportion to the Accelerations, it follows, that 
the perpendicular depths of the Tap under the Super- 
ficies of the water mull: be always in duplicate proportion 
to the Velocities required. 

The plainnefs and certainty of this truth in Hydro- 
ftaticks, long fince fo fully and excellently demonftrated 
by Stivinus of all Fluids, and fo highly improved of 
late in the particular applications thereof by many more 
modern Authors, who have writ moft learnedly and 
clearly thereof, as well as experimentally and pra&ically, 
makes me much admire at the learned Do&or More, 
who in his Enchiridion Metaphyftcum^ in the n, 12, and 
13 Chapters, and in a Book, newly publifhed, called, 
Remarks nfon two late ingenious difcourfes>8zc. does not 
only deny this Gravitation in the parts of Air, but of 
Water, quickfilver, and other Liquors. And inftead 
thereof, to folve the Phenomena, would introduce into 
the World a Principle, which he terms an Hylarchh\ 
Sprite which at command a&s and performs whatsoever is 
neceflary to folve all the Phenomena of Mechanical, Hy- 
droftatical,and,ina word,all Phyfical motionsand effe&s. 

In anfwer to whofe Dodrine about Hydroftaticks I 
fhall only urge this one Experiment of the Velocity of 
the current of Fluids, tapp'd and running at feveral 
depths under the Superficies of that Fluid,which can no 
ways be folved by the Hylarchick Spirit, and we muft be 
fain to come to the Mechanical and plain Rules of moti- 
on, and to allow every particular of that Fluid to prefs 
with its own gravity where ever placed. And this I will 
prove from his own words in his Enchiridion Metaphy- 
ficum^ pag.i 13. where explaining very ingenioufly the 
"ilypothefis of Gravitation of the parts of Fluids one 
upon another by the fimilitude of fix men (landing in a 
Line, and preffing againft a Wall, (which men he marks 
withABCDEF, and the Wall with G) He fays, that 
A the fiift man cannot prefs Fthe laft againft the Wall 



G but by preffing B againft C, and C againft D, andD 
againftE, and Eagainft F \ nor can A prefs B againft C, 
nor C prefs D againftE, nor E prefs F againft the Wall 
G but at the fame time it muft be underftood that B 
pretTes D towards F, and D pretTes F towards the 
Wall G for A C andE,fays he,are here put for Des Cartes 
Materia 'beleflh, preffing the parts of the water within 
the cores and B D and F for thofe parts of the water 
prefiL the bottom of the Veffel But iayshe, that B 
preftes D, and D preffesF appears from this that calling 
out E and F, D doth run to the Wall G and carting out 
C D E and F, B alfo will run to the faid Wall. And fo, 
favshe theftate of the matter would be if Gravity did 
proceed from the meer Mechanical motion imparted to 
theTerreftrial parts of the Fluid,by the MatmaCxlefiv 
of Des Cartes, to wit.the Elements would aftually gravi- 
tate in their proper places. But fince there is nofuch 
thine, it isafurefign that Gravity doth anfe from a 
higher caufe, which higher caufe he elfewhere fuppofes 
to bean Hylarchick Spirit. This from fo plain reafoning 
is a ftrange Conclufion, and contrary to all experience. 

Now though, I confefs, I fuppofe Gravity to be other- 
wife performed than as Des Cartes has fuppofed, yet do 
I believe his Suppofitions fo Rational and Ingenious, and 
fo much above theObjeftions brought againft them, and 
fo much better than any other I have yet met with as no 
wifetodefervetobe efteemed fadadelma, as the lear- 
ned Doftor is pleafed to term them,^. 12 5. 

It fhall not be my bufmefs to defend Des Cares Prin- 
ciples at the prefent, nor to fet up any new Hypothe- 
fisinftead thereof, but only to urge this Experiment of 
the running of a Liquor fwifter and fwifter, according 
as the hole through which it runs is deeper and deeper 
placed below the Surface of the faid Liquor or Fluid, 
and that the Velocities of thofe ftreams are always m a 
fubduple proportion to the Altitude of the Flmd above 
thofe holes i whence it is evident that the force that 
makes that Fluid run is always in the fame proportion 



With the Altitude of the fluid pans above thofe holes $ 
and confequently, that the motion of them is exactly 
according to the plain and obvious Rules of Mechanical 
motions. And confequently for the folving all the Phe- 
nomena of Hydrofraticks there is no need of any other 
Principle than the plain Mechanical Principles, which 
fuppofetL every Terreftrial Body to have a Gravity in it, 
which is always the fame, and always communicates its 
Gravity to the Terreftrial Bodies fubjefted under irj 
and not only its own, but tile Gravity of all other Bo- 
dies above it, which have com munkated their Gravity 
to it, and that this Gravitation is always the fame, and 
aeteth continually by continual repetitions indefinitely 
fwift. And that this gravitating or communicating of 
its weight, together with the weight of all other Bodies 
communicated to it, is no ways differing from all other 
communications or propagations of motion, which the 
Doctor muft confefs to be meerly Mechanical, if at leaft 
he will admit of any fuch thing as Mechanical motion. 
For I cannot conceive any Reafon why the Doctor 
- Ihould not allow for inftance the parts of a Cylinder of 
Lead to prefs upon one another as much when they are 
kept melted in an Iron Cylinder into a Cylindrical form 
part over part as when the Lead is cold and: divided 
into feverar parts, and laid one over another in the 
fame form that they were kept in by the incompaffing 
Iron Cylinder. Since if the Iron Cylinder and melted 
Lead, and the Iron Cylinder and cold Lead be weighed, 
it will be found that they have both the fame weight 
or gravity downwards, and do communicate continu- 
ally the fame force,preilure,indeavour, impetus, ftrength, 
gravity, power, motion, or whatever elfe you will 
call it to the Scale. And I fuppofe the Dodt or will grant, 
that if the cold Cylinder of Lead, weighing ten pounds, 
be divided into ten fhorter Cylinders^ that are each a 
tenth part of the whole, and do each weigh a pound 
alone, every one of the upper {hall gravitate upon every 
one of the lower $ and that the tenth, with the other nine 

upon 



(30 

upon it, (hall prefs the Scale with ten pound weight, 
andconfequently, that the tenth doth not only commu- 
nicate its own gravity of one pound, but the gravity of 
all the other nine above it, which is nine pounds 3 and, 
if the tenth be taken away, and the ninth be put to 
touch the Scale, with the other eight upon it, it is certain 
that the ninth will not only communicate its motion, or 
prefs the Scale with, its own weight of a pound, but will 
communicate the motion to, or prefs the Scale with the 
weight of eight pounds more, or of all the eight Cy- 
linders fuperincumbent, and the like Ratiocination may 
be upon the eighth, feventh, fixth, fifth, fourth, and 
fecond, but the laft will only prefs the Scale with its own 
weight, unlefs we take in the confideration of the weight 
of the Air, which in this Ratiocination is not neceP-- 
far y. Since then I think it cannot be denied but that the 
whole ten ftanding in a Cylinder one over another, the 
tenth is preffed by nine, and prelles with ten pound 
weight 5 the ninth prefles with nine, and is prelTed with 
eight 3 the eighth is preffed with feven, and preffes with 
eight, and fo onwards, and that the prefliire of the- 
loweft downward is always proportionable to the height 
of this Cylinder. Suppoiing thefe to be all melted in an 
Iron Cylinder^ but kept in the fame pbfition and fitua- 
tion, and finding the whole to keep the fame weight,, 
why fhould we not believe that each of thofe parts wilt 
exert the fame effe&s, as to gravity, on. thofe be- 
aeathitasthefame parts, cold, and in the fame pofture 
did 3 fince if the Cylinder of the Fluid be fhortned by 
1, 2, 3, or 4, tenths of its height, the fame abatement of, 
weight or gravity will appear. Having ferioufly peiufed 
all the Ratiocination that the Doftor hath produced, 
both in this late Bt><^k, ; and in hisEmhiridionMeUfhyfi- 
earn, I cannot find any tforyvirlcmg reafon againft it, but 
what feems grounded, ujpon fome pre-coneeived Notions 
and Hypothefes which I cannot underftand 3 and I -cm* 
mot fee 5 how hf can avoid acknowledging tkn to. be a 
]kkc^r^4 ; raotipai 3 if -at.leaft. he wMM$mmy?W# 

ehanicai 



chanical motion at all, fince it doth fo perfeftly, and m 
all eircumftances fo exa&ly conform and agree with the 
Laws of Mechanical motion, that I do not know any 
difference, nor any one Phenomenon of Hydroftaticks or 
Gravity but what may be clearly folved by the common 
Rules of Mechanicks. 

But to pafs by all other Mediums to prove this Gra- 
vitation or preflure of the parts of Fluids one upon 
another, I (hall only infill: upon this one Experiment of 
tiie Velocity of Fluids, vented or running at feverai 
depths below the Superficies of that Fluid. In which it 
is obfervable, that the quantity of water running with- 
in a certain fpace of time is always in a Subduple propor- 
tion to the height of the preffing Fluid above the hole. 
That is, the quantities of water are in proportion to 
one another as the iquare Roots of the (everal Alti- 
tudes. As for inftance, it is the obfervation of Merfettnu* 
in his Hydraulicks, that a Tap of an Inch bore, four 
foot under the Superficies of the water will yield a 
pound or pint of water in 13 Seconds of time 5 now, if 
it bedefiredtomakethe water run through a Tap of the 
fame bore twice as fall:, that is, to yeild a quart or two 
pounds of water. This new Altitude muft be made to 
the former Altitude, as the Iquare bf two tothefquare 
of one, that is, as four to one } whence it will follow, that 
tht Altitude of the water above the Tap muft be made 
fixteen foot to make the Tap run a quart of water in 13 
Seconds of time. And \i it bedefired to have the Tap run a 
Gallon or eight pints in 13 Seconds, the proportion of 
the new Altittide to the firft muft be as the Iquare of 
eight to the fquare of one, that is, as 64 to 1, whence 
theAkitude of the water muftbe 256 foot, and the like 
lor any other quantity or Velocity defired. As if it be 
defired that the Tap ftiouldonly run half a pint in 13 
Seconds, the Tap muft be placed atone foot under the 
Superficies, which is a quarter of the former Alti- 
tude. Now this is exa&Iy according to the General 
Jtajte of Mechjnicks. Which is, that the proportion of 

the 



(33) 
the ftrength or power of moving any Body is always 
in a duplicate proportion of the Velocity it receives 
from it 3 that is,, if any Body whatfoever be moved 
with one degree of Velocity, by a determinate quantity 
of ftrength, that body will require four times that 
ftrength to be moved twice as faft, and nine times the 
ftrength to be moved thrice as faft, and fixteen times the 
ftrength to be moved four times as fair, and fo forwards. 
This is moft certainly true in the motion of Bullets (hot 
out of Cannons, Muskets, Piftols, Wind-guns, Crofs- 
bows, Spitting-Trunks, and the like 3 as likewife in the 
motion of Arrows {hot with Bows or Ballifbe j of Stones 
thrown by the hand, or with Slings 3 of Pendulums mo- 
ved by Gravity or Weights 3 of Mufical Strings 5 of 
Springs, and all other vibrating Bodies, of the motion 
of Wheels, Flies, &c. drawn and turned by Weights 
or Springs 5 of the motion of Perpendicularly or Ob- 
liquely falling Bodies 3 and in a Word, of all other Me- 
chanicaland Local motions, allowance only being made 
for the impediment of the Air or other Fluid Medium, 
through which the Body is moved. Now if the 
Doftor will contend for an Hylarchick Spirit to perform 
all theft; he may plaufibly enough contend for it alio in 
the Experiment of the Gravitation of the parts of Fluids 
one upon another. 

We fee then how needlefs it is to haverecourfeto an 
Hylarchick Spirit to perform all thofe things which are 
plainly and clearly performed by the common andknown 
Rugesof Mechanicks, which are eafily tojbe underftood 
and imagined, and are mofc obvious and clear to fenfe, 
and do not perplex our minds with unintelligible Idea's 
of things, which do no ways tend to knowledge and 
pra&ice, but erid in amazement and confufion. 

For fuppofingthe Doftor had proved there were fuch 
an Hylarchick Spirit, what were we the better or the 
wifer unlets we alfo know how to rule and govern this 
Spirit > And that we could, like Conjurers, command this 
Spirit, and fet it at work upon whatever wejbadocca- 

F (ion 



(34) 
lion for it to do. If it were a Spirit that Regulated the 
motion of the water in its running fatter or flower, I am 
yet to learn by what Charm or Incantation I fliould be 
able to incite the Spirit to be lefs or more a&ive, in fuch 
proportion as I had occafion fbr,and defired 5 how fhould 
I fignifie to it that I had occafion for a current of water 
that fhould run eight Gallons in a minute through a hole 
of an Inch bore > If the Doctor fliould tell me, that I muft 
make the Tap at fuch a depth under the Superficies of 
the water, and then the Hylarchick Spirit will make the 
water run as I defire, I would then inquire how he 
comes to call that an Hylarchick, or matter-governing 
Spirit, which is rather commanded by matter, and fub- 
je&edtoitsLaws, and is neceffitated to aft exa&Iy ac- 
cording to the quantity and pofition of matter, by what 
means foever it be fo placed > This Principle therefore 
at bed tends to nothing but the difcouragtng Induftry 
from fearching into, and finding out the true" caufes of 
the Phenomena of Nature : And incourages Ignorance 
and Superftition by perfwading nothing more can be 
^nown^ and that the Spirit will do what k pleafes. For 
if all things be done by an Hylarchick Spirit, that is, I 
know not what, and to be found I know not when or* 
where, and ads all things I know not how, what fliould 
(houM I trouble my feif to enquire into that which is 
never to be underftood, and is beyond the reach of my 
Faculties to comprehend > Whereas on the other fide, 
if lunderftand or am informed, that thefe Phenomena 
«fo proceed from the quantity of matter and motion, and 
that the regulating and ordering of them is clearly with- 
in the power and reach, of mans Induftry and Invention $ 
£have incouragement to be ftirring and adive in this in- 
jg&tf. andferutiny, as where I have ta do withmatter 
aad motion that fell under the reach of my fenfes, and 
&awno need of fuch: Pvarified Notions as do exceed 
Imagination and the plain; deductions of ELeafons there- 



to*: what fa clfcarex. tOibe fecn and tried by Experi- 
ment, 



(35) 
menr, and what more eafie to be imagined and under* 
flood than that a Cylinder of water, or any other Ho- 
mogeneous fubftance of twice the height ihould have 
twice the gravity or preffure : of thrice the height, thrice 
the preffure : often times the height, ten times the pref- 
fure: of 100 times the height, ioc times the preilhre 
and confequently, to imagine that as in all other Mechani- 
cal motion, four times the preffure will doiible the Velo- 
city, nine times the preffure will treble it, fixteen times 
will quadruple it, and ico times will decuple it, and fo 
forward $ So in this Experiment the fame preffure will 
perform the fame effeft, and a proportionate preffure a 
proportionate effeft: And fince we find that the effect 
does moftexaftly anfwerthe Theory (as moft certainly 
evidently, and undeniably it doth ) why fhould 4c 
doubt of thecaufe which is fo certain and Regular a Con- 
comitant, that it is always prefent when the eftecl is 
performed > And where ever it is prefent, ( if other 
Circumftances hinder not) the effecl: certainly follows 
I could have gone over all the other Ratiocinations of 
the Doctor for an Hylarchick Spirit to perform the 
effefts which do clearly belong to Mechanical motions 
and powers, and are performed and regulated exa&ly 
according to the quantity and quality of matter, and ac- 
cording to the general and univerfal Laws of motion 
and not otherwife. But that is not my prefent bufinefi* 
but rather to explain how this contrivance of Poifes 
doth ferve to make a Ciftern or Veflel to run any quan- 
tity of water required in any fpace of time. And that to 
run the whole quantity either with an equal Velocity or 
ftream, or by any defired degrees to be accelerated or 
retarded from the beginning to the end, which forfome 
occafions in Mechanicks is of great ufe, and hath not 
been explained by any Writer of Hydraulicks hi- 
therto. 

I fhould have here left this Digreffion, but that I find 
a little further in the aforefaid Doftors Enchiridion, to 
wit, in the nineteenth Chapter,in the fifth, fixth, feventi^ 

F 3 and 



C#3 

and eighth Se&ions, continued from the 246. to the 2.56. 
Page, fome Animadverfions upon an Explication: of Co- 
lours which I did formerly publifh in my Mkrographia, 
from the confutation of which he endeavours to aflcrt . 
this HylarchickJSprit. But in this he doth Canen trinm^ 
phmantev0oriam o andfeemsto make very flight of that 
whichhe neither hath hitherto by all he hath (aid in his. 
Enchiridion Metaphyficum, nor can by all other Argu- 
ments he can produce anfwer. For if the Do&or had 
pleafed to have considered theObje&ions I made againft 
the Hypothefisof the Rotation of the Cartefian Globuli 9 
with a little more ferioufhefs and deliberation, he would 
not, I conceive, have believed that one that underftood 
the Qbjedion would he fatisfied with fo flight and infig- - 
nificant anfwers,, as he is pleafed to make to them> His 
Anfwer then to the firft Obje&ion which I brought 
againft this Hypothefis, which was raifed from Experi-. 
ments made with thin plated bodies, producing colours, 
though the refrafting Superficies: were parallel, is no 
more but this .-.That it is not every fecond Refra&ion of 
the Ray in a Parailelipiped that doth deftrpy the Rota- 
tion generated by the firft, but only that which cntring 
at one fide, pafleth through,, and goeth out again with 
the fame refraftion it entered. In which cafe only, fays, 
he, the Rotation of the Globulin generated ia the firft. 
$uperficies > is deftroyed in the fecond. . But, fays he,, a 
Ray falling upon a Parailelipiped, and being reflefted: 
from the fecond Superficies, fuffers a double Refra&ion. 
in the fame Superficies, the one at entring, and the other, 
at going out again 5 both which Refractions, fays he,. do 
promote the Rotation of the Globuli the fame way. 
This he fays very pofitively, but gives no reafbn for it. 
Nor indeedcould he^ fince it is exprefly contrary, to* 
Des Cartes Principles, and; to, all the Phenomena: of fuch 
Parallel fided bodies until they come to a certain degree, 
of thinnels : For if his Affirmation were true, then muft 
all Reflexions from the Quickfilver, or foil of Looking- 
glaffes, efpecially if a little oblique^ raake the Object 

fpread, 



fpread, and become coloured in the fame manner as Ob- 
lefts do which are look'd at through Prifmes. But this 
is contrary both to Experience, and the Laws ofReflefti- 
om for the Refraftions in the Parallelipiped Bare the' 
very fame with the Refraftions in the ParaUehpiped A, 
the aefleftion at D making the Ray to be redrafted at F 5 
inthe fame manner as if it were refraftedat G by G H, 
and the Parallelipiped were twice as thick, and confe- 
quently the colour generated in Emuft.be deftroyed ia 
F andconfequently produce no colours, as really it doth 
not in plates .beyond fuch a thicknefs* whereas if the 
Refradtion at F did promote the Rotation, as he affirms, 
then muft the refkfted Superficies I K not be Parallel to 
EF but inclined to it with an Angle atLM. ThenGN 
would reprefent FO, which is impoffible, and con- 
trary to the Lawa of ail refleftion, ,as he might have 
underftood if he had confidered my Demonftration 
about the Refleftions of. aGlobe. Nor will the Doftors. 
adding Sed de hat prima objeBione non eft quod Junius adeo 
foliciti cum fit in materia magk incerta ac wequali cujm 
interna rontextura videatur Globulornm motus wttis modh, 
fofjemtari. For fince all tranfparent bodies whatfoeyer 
p^duce the fame effeft,- that Subterfuge of fuppofing 
fome ftrange invifible. texture in the body of Mufiovy 
Glafs differing from that of other tranfparent bodies, 
will prove but a lame help, for this interna tontextur* 
muft be common to all, tranfparent Bodies. And why it 
(hould do it at one time, and not at another, the Doftor 
dothnowhere l (hew,,nQrfeemstounderftand. . 

Next whereas in the feventhSeftionof thefaid nine-; 
teenth Chapter he fays, Verum in. materU iUa idonea 
Gntta meet PluviaJ nullus Demonftration^ ScopofuMt 
trrorAuum eft deQloMkXar^uink^Std.vid^C^ 
h^imeniofis demonftrator mn jatkJnteUexiffe fcopnm. 
m Jmnelredebeat ipfius Demonftratio To. which I ^an- 
fwer, that I perceive by .the Learned. Doftors^endea- 
vours to refute it, that he neither underftood that,. 
nor the Laws of Reaeftion and Refraftion according 



-(38) 

to Des Cartel Hypothefis. Neque enimfatk erat probare 
( quod agnofco cum ficiffe fcite & ekganter ) RefraUiones in 
gutta pluvia Ha fieri, nt f in duobus pelluadi Paralklipipedi 
Later/bus cppofitk, faU£ effent.fed oportebat prtterca evi- 
cijje quod eodem modo refringatur radius in utrifque Lock 
quo in ParaUelipipedo A refrwgitur.hoc eft nt Radius B C 
quamvk oblique, perpetuo tamen cur rat ■ verft/s eandem ex-* 
tremitatem taminF quam inU ParaUepipedi ApuUverfuf 
extremitatem E, nam in hoc cafu Rotatio ad D diffohitur 
iterum ad F at fupra di&um eft 3 fed Demonftratio Inge- 
mofl Micrographi hue non attingit 5 fed probat fecundam re- 
ft actionem in oppofito Latere fieri admodum refra&ionk in 
ParaUelipipedo Q ubi Radius B N primo refringitur in D 
&procurrens verfm extremitatem E ibique inflexus pcrgit 
pojfea verfus alteram extremitatem G & RefringiUir in F f 
qu£ refra&io non diluit Rotationempriork refraUionk in D* 
. qnippe quod tendentia Radii (it in partem oppofitam. If 
the Learned Do&or had better confulted Des Cartes 
Do&nne, or the common Laws ofRefleftion and Re- 
fraction, he would have been of quite another mind, and 
would not fo pofitively have aflerted a Propofltion Co 
pofitivety contrary to the Principles of Des Cartes and 
all Experiments. For if what he affirms were fo, then 
(as I urged before) according to Des Cartes Doctrine 
and the Do&rine he would defend, the Image from a' 
Looking-glafs mult be returned coloured, and the fame 
alfo from a plain fided Prifme, where the refracting fides 
are Perpendicular or equally inclined, but contrary ways 
to the Refle&ing Superficies. But this is contrary to 
Experiment, hemuft therefore once again confiderhow 
to find out a Reafon why-there is no colour generated 
where, according to his AfTertion, there is fo great a re- 
fraction, and a doubly promoted Rotation made in both 
the refracting Superficies the fame way, and both fo 
much promoting the faid Rotation of the Globuli. He 
might therefore, if he had pleafed, have fufpended his 
Conclufion. Adeo nt DoUrina Cartefiana de Globulk to- 
mmque Rotatknibus nihil periclitetur ah hac Demonftra- 

tione 



(39) 
tione epi£ quamvk fatk elegant fit & concinna, debitum ta- 
men fcopnm non omrnho attingit] until he had a little far- 
ther confidered the nature of Reflexion and Refraction." 
Now, becaufe I find that the Learned Doctor is not; the 
only perfon that hath not rightly apprehended this 
Theory, give me leave to explain a little more particu- 
larly the manner thereof: Suppofe we then in the three 
Figures D E and F, that the (pace between the two 
Parallel Lines a c and b d doth reprefent a Ray or Radia- 
tion of light 5 Not a Mathematical Line, but a Phyfical 
one of fome Latitude, between which Lines is propa- 
gated a motion, or fomething equivalent thereunto, 
which ferves to produce the efFeft of light. This motion 
wefuppofe to be propagated by a Pulfe or Wave In all 
uncoloured Rays at Right Angles with the Line of Di- 
rection, but in coloured Rays more or kfs obliquely ac- 
cording to the greater or lefs refraction. We will fup- 
pofe the ftroke of the Pulfe to be the length of the fpace 
between i and. 2, or 2 and 3, or 3 and 4, dv- and con- 
sequently, in a uniform medium the pulfe will continue 
the fame, and the expanfion of it will be Perpendicular 
to the Line of Direction or progrefs 5 but when it comes 
tothe Refracting Superficies c d, Obliquely the fide of 
the Pulfe c touches the refracting Superficies firft 5 and be- 
ing propagated into the refracting medium by a longer 
and quicker Pulfe, it is propagated to 4 below c before 
the other fide of the Pulfe touches the Superficies, at d, 
the Pulfe therefore 4 4, 5 5, 6 6, &c. becomes Oblique 
to the tendency of the Radiation 3 and by the Superfi- - 
eies-e fit is reflected by 7 7, 7 j r 7 7, till it touches the 
fccond refracting Superficies gh 5 where it is-obfervable, , 
that the fame fide of the Ray that entred firfi the Super- 
fieies c d enters firft into the Superficies g h, in the fame - 
manner as if it had proceeded on by the ftraight Lines f m * 
el till'it met with a Parallel Superficies lm -to the firfi: : 
c d 5 for the Ray between the two Parallel Lines f ii,\ e g 9 \ 
hath the fame inclination and refpecl; to the Refracting : 
Superficies hg, that the Ray= between fm,andkl would.; 

have... 



(4o) 
have to the Superficies m 1, fuppofing there were So Re- 
nting Superficies ate f. I '{hall not need, I hope, more 
particularly to demonftrate every part of this Explana- 
tion, the very obferving the Delineation of the Scheme 
being enough to make it plain to any one never fo little 
verfed in Geometry, from which he will plainly per- 
ceive that what I endeavour to demonftrate was really 
fo, and that I did underftand what fcope my De- 
monftration aimed at, fo far as to hit the Mark, which 
was to (hew that Colours were generated, where, ac- 
cording to Des Cartes own Principles, there could be no 
Rotation of the Globuli. Now, though the Learned 
bo&or would not admit of this Demonstration to be 
fufficient to do the work, yet he fays, Prfg.252. Verun- 
tamen dtflitrnthndnm non ej?, non pauca pte meapte opera 
excogitajje qwbus pro perftiafijjzmo habeo eorum motus. & 
rot att ones modk pure mechanic fs femper fieri nonpoffe. And 
in profeeutionof thedeftruclionof this Rotation of the 
Globuli, which he hath hitherto feemed to defend, he 
adds four feveral Arguments, I (hall not now ftay to re- 
peat them. But whofoever will pleale to read what the 
Learned Doctor hath fuapte opera excogitated againft the 
Cartefian Hypothefis, and fet down in the 252, 253, 254, 
and 2 5 5. pages. And compare them with what I have 
faidintheforementioned place, to wit, at the latter end 
of the 60. and the beginning of the 61. pages of my, 
Micrographia, may plainly find the Arguments brought 
by the Do&or do very little, if at all, differ from thofe 
I there publifhed. 

I could heartily therefore have wifhed that the Lear- 
ned Do&or had made ufe of fbme other Mediums to 
prove the Exiftence of an Hylarchick Spirit, and not 
have medled with Arguments drawn either from Me- 
chanicks or Opticks 3 for I doubt, that fuch as underftand 
thole fubjefts well, will plainly fee that there is no need 
of any fuch Hylarchick Spirit 5 and if there be no need 
of it, but that all the Phenomena may be done with- 
out it, then it is pj:ohable that there is none there, for 

Natura 



(4i) 

Natwanihilagrt Jrkpa. Ithad been much eafier to have 
proved the exiftence of it by Arguments drawn from fub- 
leaswelefsperfeftly underftand, as from the generati- 
on nutrition vegetation, and propagating of Vefetables, 
mid animal fubftances; for there the manner of theprogrefs 
of Nature being infinitely more curious andabftrufe, and 
further removed beyond the reach of our fenfes and un- 
derftandings, one may more boldly affert ftrange things 
of this Hylarchick Spirit without fear of controul or 
contradiction, and from whence pofSbly it mayneverlie 
within the power of Reafoning to banift him. 

But to leave this Digreffion, and return tothjsufeof 
theie water-pones. 

fA^S eff f m / y be ^^^g and refining of 
Earth, Clays, Powders, and the like ; the clear wate? by 
thefe contrivances being made to run over gently at the 
top and fo leaving all the fettlement fronuhe wateiat 
the bottom. 

By any one of thefe, with a receptacle Ciftern added 
to* the ftreamof water from that Ciftern may beaaS 
Jeratedor retarded by any degreesdefirable.This doth de- 
pend partly from the proportion ofthe Tap of the Recep- 
tacleCifterntotheTapofthecounterpoifed Ciftern, and 
partly from the (hape and make of the Receptacle Ciftern 
by the proportion and ftape of which the ftream of Li- 
quor through the Tap ofthe Receptacle Ciftern may be 
modulated at p eafure, as any one, a little verfed in Hy! 
droftaticks, will eafily perceive and demonftrate. 

r Afi^effea may be for governing the heat of Lamps 
for Diftillations, Digeftkms, Fermentations, PutrS 

StaS^S f^r"* ^ % S -° f Birdsor »2&» 
accelerating and feafomng, or timing the growth of 

Plants; nealingof Glafiesand Metals by the |adual at 
cefs ofthe heat, fo as to make them fit for ftronger 

O degree?;, 



degrees, or by the gradual recefs to bring them out of the 
greater degrees to make them tough and capable to re- 
ceive the cold of the Air. 

It would be tooiongto give inftances of contrivances 
for every of thefe operations but the skilful Mechanift, 
Philosopher or Chymift wilt eafily fupply his own defires 
by fome one of thefe I have inftanced in, or at leaft by a 
compofition of them. I ihall therefore only add a defcri- 
prion of a Clepfydra or time-keeper or two 3 and fo leave 
this fubje&fortheprefent, 

— ¥ ; _ 

'A defcriptkn of a new fort of Clepfydra* 

TUh contrivance is nothing elfe than that Two of the 
fecond fort of Veflels are fo contrived as to rua 
Into each other and to empty themfelves and be filled al- 
ternately, and their bignefs or capacity and the hole 
through which the Liquor is vented are fo proporti- 
oned as. to be emptying the fpace of an hour, which is 
eafie enough, and may be adjufted to-what accuratenefe 
is defired. Then the convex Superficies of the Cylin- 
drical poife is divided into fixty equal parts by ftraight 
LinesdrAwn upon its Surface Parallel to the Axis, and to 
each others thefe lines by. the finking or turning of the 
faid poife denote the minutes, and if Imaller Divifions 
of time be defired, the (paces- between them may be di- 
vided by other fmaller Parallel Lines -denoting the parts 
of each minute to what nicenefs is defired. One of thefe 
Cylindrical Receptacles may be fixt, and the other by an 
eafie appar at /&, may be made to rife a little when it is top- 
full, and fall a little when quite empty below the Level 
of the other that is fixt: The Chanel between-them, 
through which the water is to run out of the one into the 
other, may be a finall pipe with a hole in it of a bignefs 
frojortioned, asl (aid above, to let the Liquor run out 

of 



C43) 
of one into the other in the time defired, and its ends 
maybe faftned to the two Receptacles by a part of the 
neck of a bladder or gut, fo that it may be limber, and 
may always have a Declivity into the Vefiel that is to be 
filled 5 the Declivity need not be above half an Inch. 
The Liquor ufed ink may be Water, Oyl, or any other 
Liquor that doth not eafily evaporate : But the belt of 
all is Quickfilver, becaute it doth not with keeping eva- 
porate at all fenfibly, which I Jbave carefully obferved 
for thefe fifteen years laft paft. Nor doth it grow thick 
or foul by the alteration of the Air, pbr do I find it fen- 
fibly alter by the heat and cold, at lett not comparable to 
the great changes which other Liquors fufFer by the alte- 
rations of thofe qualities. It is an excellent material for 
meafiiring time in a ftanding Machine 5 and there may be 
hundred of ways contrived to make itmeafurethe fpace 
thereof as accurately as a Pendulum 5 and I have many 
times admired that Tycbo Brake, who was otherwife \o 
curious and exaft in the contrivance and make of his En- 
gines and Inftruments, was yet fo defe&ive in his con- 
trivances of meafuring time by Quickfilver,when there 
were lb many obvious and eafie Ways of doing it, as he 
feems to complain in his works. I have made trial of 
feveral with very good fuccefs, and found fome of them 
even beyond expe&ation certain, of which I may here- 
after upon an other occafion add the defcriptions, when 
Ipubliui the various ways of making exaft Time-keepers 
or Watches. In the mean time, being now (peaking of 
Time-keepers, for variety fake I fhall mention. 



T J Mew frinci^efor Watchu. 

THis is a way of regulating both {landing Watches,andl 
movable Watches,either for the Sea,or the Pocket, 
Which fome ten or twelve years fince I fhewed the Royal 
Society jwhm I (hewed them my contrivances of the Circu- 

G 2 hi 



lar Pendulum, which isfince publifliedby Monfieur Huge* 
#;** 5 which is alfo menrioned in the Hiftory of the (aid Se* 
i7*e^ 5 p.247.1in.20.Thiswas by a fly moving Circularly in- 
ftead of aballance^whofe motion was regulated by weights, 
flying further and further from the Center according as 
the ftrength of the Spring of the Watch had more and 
more force upon its Arbor. The Weights were regulated 
from flying out further than they ought todo by the con- 
trivance oFa Spiral Spring,drawing both the faid Weights 
to the Center of the motion or fly,in the fame proportion 
*sl then demonftrated Gravity to attraft the weight of a 
Circular Pendulum, moved in a Parabolical Superficies, 
toward* the Center or Axis of its motion. The Weights 
werefo contrived as always to counterpoife each other. 
The Skeleton of this fly you have reprefented in the 
Eigure. The particular explanation of the parts, and 
the Geometrical Demonstration of the Principle both of 
the Springs* and of the flying from the Center, I 
fhall explain in the Theory of Springs, and in the de^ 
feiption of Time-keepers and Watches- 

Ol StijLUQVpyi vLCLfmtOK&ja^p™ opy&vov %pvwQ\m$nnv dp%twp 3 



An OhferVation about the Seed ofMo/} 9 . 

Since the publishing of my Micrography, I have met 
with an Obfervation,wlxich though it be of one of the 
fmalleft compound bodies I have hitherto, taken notice of^ , 
yet does it afford a hint of very great-concern in Natural 
Philbfophy 3 And it does feem ta make clear the caufe o£ 
^Phaenomenon,. that hath appeared dubious,not only to 
me 9 , but to many other more knowing; Naturalifts* I have 
often doubted, I confeiS, whether Mofs,,Muftiroms,and fe^ 
^ralpth^r fmrilPlams ( which the Earth Teems to pro-. 



duce dumfj&™S) Wetethe ofF-fpring of a Seed or Grainj 
and I have been apt tvObelieve y that they were rather a 
fecondary production of Natures being fomewhat the 
more inclined' to that opinion, becaufe having formerly; 
examined the (mall knots or Seed-cods of Mofs with a 
fingleMicrofcope, I could not perceive, any thing in them 
that I could imagine to be$eed,at leaft not to great a quan- 
tity as feemed neceflary to maintain fo numerous a Pro* 
geny, as was every where to be found of it - 7 that, which 
then came out of them, feeming to be rather a pulp or 
pith, than any thing like the Seeds in other fimilar Cods* 
But being fince fomewhat more inquifitive, Idid exa-? 
minefeveralofthe above-mentioned Knobs or Seed-vet 
fels, and found that there, were feeds in them* no leg) 
wonderful for the greatnefs of number, than the final- - 
iiefsof bulk. Takingithen fomeof the ripe and brown 
or reddifli ones of them, and preffing them < pretty hard,, 
i found, that, there was a fmallduft went out of thenv 
which feemed to vaniih into the Air. Preffineand fquee- 
zing others of thefe upon a black plate, and examining 
the powder with a Microfcope, I found it to be a great 
heap of exceeding, imall Seeds, \ Globular, and pretty, 
tranfparent. It is the fmalleft, I confefi, I have yet fezn^ 
and, it may be, that has hitherto beeadifcovered. And 5 ; 
imlefs that be a plant, which Tdifcovered. growing on. 
die blighted leaves of Rofes, and :that thofe fmall bodies- 
be.feed veffels $ or, unlefithofe Knobs,, I have difcovered. _ 
on the top of mould, be the like ^ I cannot prefeutly 
imagine where there fhould be found afmaller. For, I 
find, that there will need no lefs than thirty fix hundred/ 
of them to belaid one by another in a line,to make the ■■» 
lengthof an Inch 5 and, to cover the Superficies of an ' 
Jnch-fquare, there. will need no lefs than nine hundred- 
andthreefcorethoufands, befides twelve millions,* of fn>> 
gle Seeds if laid quadrangularly, but if laid triangularly^ 
there will .need no lefs than two hundred and fourfcore. 
thoufand, befid.es Seventeen Millions of fingle grainsv 
And the number in; a. grain weight of them cannot be 



"40 - 

lefs than One thoufand three hundred eighty two Million* 
and four hundred thoufand (ingle grains, about eighty 
of thefefquare Superficies of Seeds being laid one upon 
another in the Trigonal order, making, as near as I can 
guefs, the thicknefs of a piece of fine Paper, a fquare 
Inch of which weigheth a grain; And though this 
may &^ a moft incredible narration $ yet I would 
defirefuchas are apt to be too cenforious, to take the 
pains to gather a few of thefe Seed-veffels, and examine 
them as I have-done, and then (peak what they find, and 
believe no more than their own] fenfe and reafon will 
inform them, and they - may eafily fee, that what I have 
afferted, will be rather ihort of than exceed the real num- 
bers. Now if this Shell of the Seed be thus fmall, how 
much (mailer' muft needs be the rudiment of the Plant 
that lies enclofed within it > And how eafily may fuch 
Seeds be drawn up into the Air, and* carried from place 
and place, even to the tops of the higheft Towers, or to 
places moft remote, and befowed by the paffing Air, or 
falling drops of Rain, on the boughs or branches of 
Trees, fides and tops of Walls, Houfes, or Steeples ? 
And it is not in the Art of man to leave Earth expofed to 
the common Air, and to exclude the entrance, or prevent 
the lowing of thefe imperceptible Seeds j and therefore 
it is not to be wondred at, that, if any earth, though 
never 4b pure, be expofed to the Air and Rain, though 
at the top of a Steeple, it will produce Mofs. 

Further inquiry may poffibly inftrud us, that there 
may be Seeds of Mufhroms, Mould and other Vegetables 
of as fmall, if notfmaller, bulk, which may be difper- 
fed and mingled with the Air, and carried to and fro 
with it, till wafhed down by the falling drops of Dews 
or Rains 3 which, if they chance to light on a conveni- 
ent foyl, do there Vegetate and (pring up 5 but dye and 
perrfh, if the ground, they lighten, be not natural and 
agreeable. But whether this conjecture hit right,further 
Mobfervation muft determine. 

This 



This difcovery I made the year after the late Fire of 

London, to wit, in the year 1667. there being then vaft 
quantities of it to be found every where diiperfed among 
the Ruines left by that Fire, which made me, I confefs 
very much wonder at firft how fuch vaft quantities fliould 
come to be then fo fuddenly rooted, and was the oceafi- 
on of my more ftrid examination of it. This I prefently 
fliewed to many of my, Acquaintants, and the next 
year 1668. upon the eleventh of Jnne I brought an ac-- 
count of it into the Royal Society, where I fuppofe it may 
yet remain upon their Regifter 5 and it was not a little 
lurprifing to all that faw it, when they confidered how 
exceedingly fmall each particular Seed was, and yet how 
infinitely vaft the number of them was produced by each 
Plant. How pxodigioufly fmall the firft beginning and 
rudiment of that Plant muft be that was produced by it j 
now, though indeed the Plant it felf beoneof thefmai- 
left,yet this Seed of it was much irnaller in comparifon 
to the Plant than the Seeds of moft other Plants compa- 
red with theirs. But about two years after this I re- 
ceived from a very good friend of mine ztBrikok the 
Ingenious and Inquifitive Mr. W. C. a Relation of fome 
kterdifcoveriesof his, which feemed much to outftrip . 
even this, whether the comparative magnitude of the 
Plant, and of the Seeds, or the number of the Seeds, or 
the curiofity of the Seed-boxes, or the ftrange way of J 
lowing and difperfing, or the place and manner of the 
Seeds production be confidered. As they were fent to 
me by him in a Letter from Briftol, dated September §d 
1 66%. take them in his own words and defcription. 



lOtmthJlanding my many -other Avocations, variety of j ' 
l^j discoveries doalmofi every day. Marge my experience $ 
but more eftecially this lap WeeK I was very, happy in the . ■ 
dete&ing of that which :all\the Philosophers and Phyficians i 
rf former Jges, have been ignorant of^aswe^may^ellama- - 
pmfromwhcit remains we have of them, My. Difcovery in ., 
Jlwmvasjhky that all the Iqndscrjpecies of Ferns together- • 



mi 



'(48) 
&Hh all the like Capillary Plants their Congeners are (though 
generally denied to have any at all) more abundantly political 
in Seeds than any other Plant befide, ejpecially the common 
Female Ferns or Brakes, and thofe more elegantly formed 
(Imean chiefly in the little Fifties contenting the Seed) than, 
many other 's, among the hundreds I have dbferved. To make 
it demonfirable to you,! have now fent you both the Plants 
with the Seeds on them, and the Seeds of the fame Plants 
apart in Papers by themfelves, which I took off from other 
Plants of the fame kind, having plentiful parcels of each 
(excepting of what Thave not fent you) this being thejeafon 
$fperfe&irig their Seeds. I thought to have fent you draughts 
of <the Seed Fijfels, as they appeared prefently after gathering, 
hut could not. I pre fume fome oftheFeficles or little boxes 
way remain whole, fo that by your Microfiche you may fee 
their 4rue figures and difiin&ions, fome ofithem being more 
flatted on each fide the little ring or cmbojfed girdle encom- 
fajfing them, others more fweHing. 

Aljo thofe little rings or bands encompaffing the boxes are 
different, in fome of the hinds broader and flatter, in others 
rmnder, and fianding up higher, yet all agreeing imthe 
principal parts of their form. I pnrpofe to draw the figures of 
them all. as they appear by the Microfcope, -together wit ht heir 
Seeds, and to add defer ipt ions of all circumfiances confide- 
rablel and joyn them to the reji of my draughts of that kind. 
Some particulars moji confiderable I now give yon in the fat- 
following account* 

1. the Utile boxes containing the Seeds are in nfofi of 
■ thefe Plant snot half, and in fome not above one third, or one 

garter as big as a very fmall grain of common white fand^ 
appearing like little bladders infolded with rings or bands, 
Jhaped like certain little worms I have met with, which maybe 
referred to theTeredo's and Eruca's. 

2. Asnear as I could compute, feme of thefe bladders con- 
tained about ioo Seeds, which were fo exceeding fmall, as to 
fo wholly inviftble to the nakedeye, and indifcoverable without 
4 Microfcope. _ 

3- Tb* 



(49) 
3- The Leaves of both the Ferns, efyecially the common 
Female pern, (which is more abundantly flored with Seed 
than any of the rejij and the other I now fend you, being kept 
clofe without brmftng, and foon after gathering expofedtothe 
Sun, or dry Air, the bands of as many of them as are ripe, 
Will contrail themfelves and break,, and fling their Seeds _aU 
about, after the fame manner as fome other fmall Plant s,fuch 
^//tfPerficariaSiliquata, and fome of the Cardarainas are 
obferved to do. This I have obferved with a fingte convex 
glafsas well as with the Microfcope, but with the latter only 
I could difccver the falling of the Seed. And a pretty quantity 
of the Seed being rubbed or brufied off from the Leaves upon 
a fine piece of Paper or Parchment, an dfweeped together into 
aheap, many of thofe boxes breaking together, and jufiling 
one another would makg the heap feem, as it were,full of Mites 
or living Creatures, even to the bare eye 5 and if the place be 
fiee from noife, and the Ear be clofe applied, the crackling of 
them upon breaking may eafily enough be heard, and upon 
running over the Paper with a Microfcope the Seeds will be 
found difterfed, and thrown at a great difiance. 

4. The figures of the Seed-veffels, as alfoof the Seeds of all 
the Ferns and thoje their Congeners, called Capillary Plants, 
are very near of the fame f ape and fize, notwithfianding the 
vafi difproportion between them, as particular common Fern, 
Wall Rue, HartsTongue, and Ofmond Royal, the firfl three 
of which being very remarkable for their unlikenefs to each 
other, andthelafi chiefly for its excelling fo many thoufand 
times in magnitude that of Wall Rue. Which obfervations may 
feem to confirm the opinions of fome learned Botanifls that 
the affinity of Plants are to be judged by the figures of their 
Seeds. 

5. That Ofmund Royal, which excellet hall the other Ferns 
both in greatnefs, comlinefs,.and vertues, and which hath 
been accounted barren, with the reft hath Vejfels and Seeds of 
the fame figure with the other, and very near of the fame 
fize, the extreme fmalnefs of which, even to invifibility, and 
the greatnefs of the Plant, one root whereof, with all the 
growth out of it ^ I have found weighing ten pounds and bet- 

H ur % 



(5o) 

m\h furpajjingly more wonderful than that ofMofs Seeds § of 
which I have fame kinds of them bearing Seeds, that a great 
number of them, with their Roots, Stalks, Leaves, and Seeds, 
do not weigh a Grain. Be fides, I have found of the common 
Female Fern fome which have been from the Roots to the ut- 
mofi top of the Leaf nine foot high, and within theft three 
days meafured the common broad-leaved Male Fern fix foot 
and an half long $ fome of the Leaves of which are' among 
thofe I now fend you. 

6. But that which appeared mofi admirable, both to me 
*nd fome other Gentlemen that were witneffes of it with me, 
was the many differing kjnds of fm all living Creatures, wholly 
inviflbletothenakedtye, and even through largely magnify- 
ing fie&acles, though fome of them were to be feen through a 
deep Convex glafs 5 but with a Microfcope, when the Plant 
was newly gathered, they might be feen nimbly runningup and 
down among the Seed-veffels, and fome of them were fo 
fmall 06 not to be above twice as big as the fmall Seeds in 
the bladder s\ a defcription of fome of which I may hereafter 
jendjou. 

I have inch fed in the box fent you twelve forts of Plants 
of this tribe, being the greatefi part of the number, and only 
feven forts of the Seeds 5 thofe wanting are the Cetrach, Wall 
Rue, Maiden-hair, and Polypody, of which notwithfiand- 
ing you may fatisfe your fe If in the mean time till I can 
fend them green by thofe fmall parcels of the Plants which 
you will fnd among fi the refi, though by keeping they are 
withered. 

The Seeds of the Ferns through a very excellent Micro- 
fcope appeared of the bignefs of a fmall Fetch or Seed of Len- 
tiles to the naked eye, and fome of them firing like the fides 
of white Peafe, with fmall regular fyobs and hollows. Thofe 
of Polypody are differing in colour andfhape being yellowijh, 
as the others are brown, red, and formed like the Seeds of 
the fmaller Medicos that is of a Kidney fiape. All the refi 
J found very near of the fame form. I cannot omit what! 
cbjerved in Cetrach, which Plant I have heretofore often con- 
sidered, and wondred atthe ill-favcuredrougknefs on the un~ 

der 



derfideof the Leaf, appearing like the flefy fide of tannd 
Leather, being wholly ignorant what Nature meant in it, but 
now by my Microfcope I find it a very pleafant objeU differ- 
ing font all the reft, wherein the curiofity of Nature ( in a 
Plant fo abjeU as that appears ) is ftewn beyond imaginati- 
on. This, when ftefi gathered, and not bruifed, appears 
through the Microfcope like fine thin Membranes, fuch as the 
Wings of Flies, chequered with figures after the manner of 
Honeycombs when the cells are full of honey, and do fed with 
Membranes, amongft which, as in fo many Cells, lie the Seed- 
veffeh, fioaped as before is mentioned. I doubt not hit you 
have read the ftrange ftories and fabulous conceits of An* 
thors about Fern Seeds. But Parkinfon is more Orthodox in 
fome things than any of them : For he pofitively concludes 
from Gen. I. ri, 12. that all Plants have their Seeds, and 
confeauentlyFern^ where if he had ft aid, he had afferted a 
general truth : But in coming to particulars, he ajprms as 
great an untruth, in faying, fol. 1036, and 1037. that the 
Seedisripe at Midjummer, according to the old traditional 
Fable, and tells how it may be gathered 5. whereas now is the 
veryfeafon of their feeding, and at Midfummer this and the 
reft are not come to their full growth, before which no Plant 
feeds. That duftinefs which he fpeaks of, and calls the Seed, is 
no other than what is found on divers other Plants, being an 
irregular Duft, and is not found on the borders of the dents 
of the Leaves on the under fide, on which the Seed grows, 
but all over fir in kjed on both (ides, and not found when it is 
fully grown. This he affirms of the Male Ferns, which are all 
differing very notably from the common Female Fern, con- 
cerning which the fabulous tradition is held. But after in 
the following Chapter of the Ferns and their Relatives now 
fentyou, he feems to give over his Scripture Proportion, and, 
Jpeakjng of the Seeds, fays no more but that they have fpots, 
dafhes, fcales, or marks on their back; fides. And of the Of 
mund Royal ((peaking of the bufi at 'the top of the Plant ) 
fays it is accounted as the Flower and Seeds. And of theLo- 
chitis afpera fays plainly they have none at all. Of this laft 
I am yet to enquire, but doubt not I ft all find that it hath 

H 2 Seed 



Seed like the reft. Of all which Gerrard and johnfbn hk 
CorrigHor gravely concludes ( having indeed no demonstra- 
ble ground to the contrary ) that fame have been too raft in 
affirming Ferns to have Seed. I intend next Summer to ob- 
Jerve whether theft hitherto unknown Seeding Plants have 
Flowers. In the mean time I am, &c. 

Eriftol. Septem- JZf f 

ber 30. 16651. • L/ • 

♦ 

Macula in Sole. 

DUring this laft great heat of weather in June I obfer- 
ved a very confpicuous Macula with its immediatly 
incompaffing Nubecula, and fome other lefs confpicuous 
Spots at a further diftance pafs over the Disk of the Sun, 
and found that it was neareft the middle when the heat 
was greateft, that the heat increafed as it came nearer the 
middle, and. decreafed as it departed from it. It may be 
therefore worth obferving for the future whether the like 
weather do not happen upon the next appearance of the 
like Macula, finceit feems not very improbable to fuppo^ 
that the body of the Sun it felf may be much hotter when 
fuch eruptions appear, thofe Macuteoften times ending in 
Faxute. And the rather becaufe I am informed that this 
extraordinary heat hath notJ^een peculiar only to Eng- 
land but very general to Europe 3 what it hath been to 
other parts of theworld further intelligence will inform us. 

Upon a fecond appearance of Spots in the Disk of 
the Sun at the latter end of July and the beginning of 
Auguft, when at one time, to wit, July 2 9. there appeared 
about iix greater and fmaller in one knot with their proper 
Nubecules or Umbra's, the heat of the weather again 
increafed to a very great degree, and abated as they drew 
toward the Limb, and grew fainter. But it hath now 
fincethedifappearing, vi%. on the fourth ofAuguft, beep 
exceeding hot alfo, though I do not find any Spots this 
feventhof Auguft^ it may therefore poffibly be that other 
parts of the body of the Sun may have an extraordinary 

; inflammation * 



(53) 
inflammation which may caufc fo fervent and Lifting heats 
as have hapned this Summer. At lead this Hint may 
dcferve fome farther Inquiry, for though probably it 
may not be attained to piedift the appearances of thofe 
Spots, yet poffibly the appearances of the Spots may 
ferveto predift the future conftitution of the weather. 
At leaftit feems worthy remarking that thegreateft heat 
thathathbeeninthe Air this year was on that day of June 
when the firft Spot was near the middle of the Sun. 

T He Publisher of Tranfa&ions in that af October 
1675. indeavdurs to cover former injuries done 
me by accumulating new ones, and this with fo much 
paffion as with integrity to lay by difcretion^ otherwife 
he would not have affirmed, that it was ascertain that 
none of my Watches fucceeded, as it was that I had made 
them feveral years ago : For how could he before of a 
Negative? Whom I have not acquainted with my Inven- 
tions fince I looked on him as one that made a trade of 
Intelligence. 

Next whereas he fays I made them without pubhihmg 
them to the world in Print, he prevaricates, and would 
have it believed that they were not publiihed to the 
world, though they were publickly read of in Sir John, 
Cutlers Le&ures before great numbers at feveral times, and 
though they were made and {hewn to thoufands both 
Enghlh andForeiners, and writ of to feveral perfcns ab~ 
fent and though they were in the year 1665. in the Hi- 
ftory of the Royal Society publifhed to the world in 
Print, becaufe, forfooth, they were not printed in his 

Tranfadions. - ■ '''-•' \ 

Thirdly, whereas the Pubhftier of Tfanfactions makes 
a Ions; ftory of my feeing his Journal Defeavans, and my - 
defirmg -to tranfcribe that part of it which concerned 
this matter, as if I had requefted fome. Angular, favour,, 
thereby. Ianfwer, frft 



(54) 

Firft, that he knew Idefignedprefentlyto have -printed 
it with Animadverfions, but he endeavoured to prevent 
me defigning firft clancularly to get a Patent of it for 
himfelf, and thereby to defraud me. 

Next, I fay, I had a right without his favour to have 
feen,perufed,and copied it, as I was oneofthe Royal Socie- 
ty, the intelligence he there brings in being the Societies. 

Then it is denied that the Defcriber of Heliofcopes 
well knew that the Transcriber of Intelligence would pub- 
lifti it in hisTranfa&ions, though it was believed if the 
publifhing it would injure me it would not be long con- 
cealed 5 which was the fole reafbnof Printinginthe fame 
Tranfaftions, viz. 112. a Letter which he had feveral 
years before. 

Thirdly, Whereas he aflerts that feveral difcoveries of 
the Accufer had been vindicated from the usurpation of 
others. It is anfwered, the clean contrary is upon good 
grounds fufpe&ed from the Publication of a Book about 
Earthquakes, Petrifactions,^. Translated and Printed 
by B. O. the manner of doing which is too long for this 
place. Such ways this mifcinformer hath of vindicating 
difcoveries from the ufurpation ofothers. 

To his upbraiding me with his having publifhed fbme 
things of Mine 5 I anfwer,he hath fo,but not fo much with 
mine as with his own defire, and if he fend me what I 
think worth publifhing I will do as much for him, and re- 
pay him in his own coyn. 

Laftly, Whereas he makes ufe of We and Us ambigu- 
oufly, it is defired he would explain whether he means 
the Royal Society, or the Pluralities of himfelf If the 
former, it is not fo, as I can prove by many Witnefles} if 
the later, I neither know what he is acquainted with, or 
what has been imparted or explained to him. 

So not defigning to trouble my felf any further with 
Lim, unleft he gives me occafion, I difmifs him with his 
— Speque metuque 
Procnl hincprocnl ito. Ho. 

FINIS. 



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LECTURES 
COLLECTIONS 

Made by 
ROBERT WOKE, Secretary of the Royal Society 

COMETH 

CONTAINING 

f Obfervations of the Comet in April, 1 6yj. 

I Fragments of feveral Lectures about thofe of 1 66 4. and 1 66 f. 
Sir Cbr. Wrens Hypothefis and Geometrical Problem about 
thofe Comets, 
A Difcourfe concerning the Comet of 1677, 
Mr. %/e's Obfervation made on two newPhofphori of Mr* 

Baldwin^and Mr. Craft. 
Mr. Gallefs Letter to Mr. Cajpni, together with his Obferva- 

tionof $ fuh 0. 
Mr. Cajpn? Reflections upon thofe of Gaffkndus^ and Hevdim^ 

and upon this. 
Mr. Hallys Letter and Obfervation of the fame made at 

St, Hellena. 
Mr. Caflinfs Obfervation of the Diurnal motion of # , and 
i other changes happening in it. 

MIC%OSCQT IV M 

CONTAINING 

fMr. LeeurpenhoecQs two Letters concerning feme late MicrO- 

Ifcopical Difcoveries. 
The Author's Difcourfe and Defcription of Microfcopes , im- 
«i proved for difcerning the nature and texture of Bodies, 
I P.C/#r»£i««'sAccufationsanfwered. 

I Mr. Toungs Letter containing feveral Anatomical Obfer- 
L vations. 

LONDON: 

Printed for J. Marty n, Printer to the Royal Society 
at the Bell in St. Pauh Church-yard. 167B. 



VIRO PERILLUSTRI 

D- JOSBTHO WILLIAMSON 



EQUITI AURA TO, 

Sereraiffimo CAROLO l\°. 

- ■ 

Mag. Britan. Fran. & Hibern. 
R. E G I, 

A GonfiBs Secretioribus , # a 
Secretis Status, 

Nee non 

SOCIETATIS REGALIS 

L0HS >I KPHJ IS ^ 

Ad Scientiam Naturalem promovendam 

P R JE S I D f 

DIGN1SSIMO. 



NE C potui, nee dtbui, Nobiliffime Vit , c«- 
jufquam alius nomen his Chartis inferibere, 
pater Tunm.SubTe nat<e,Tibi Vitam debent j Ti- 



H (^^M^m^ikam^dm. Bgiegius ilk 
Tuus animus ad inJiaurandamTHlofopkamar^ 
adeo omnes utiles^ihihomin^dlioquhifukimido^ auda- 
ciam hujus dedkationis feck. Egop* nunc fotuirfro- 
fero, magisad Gratuktionemojiendendam, quam erudu 
tiomm. Spero autem , quemadmQdum fub Tuo 
$^J£SI'1>I0 major* indies Augments Scienti- 
arum in bac gente fiunt, ita exorkuros vires doElos, 
qui Tibi jujla precoma laudum perfolvant ; quod ego 
p& tenukatene conari quidemaudeo y quanquamcum 
primis Jim 



Dignitatis & Honoris Tui 



Studiofifltmusj 



RoBERTUS HoOKE* 



SY^CP^ 



ST NO P S I S. 



THEGomet feen Apfilzi. 1677. between the Triangle 
andtheClbudof V, its tail not dire&ly oppofite to the 
©, its Magnitude , Brightnefs, Head, Nucleus, Blaze, 
(1. J Why fometimesuHorter,fometimes longer-, without fcnfible 
motion of parts, explanation of the firft figure, as feen by the eye. 
(2.) Of the fecond Figure, as feen through a glafs, of a parabolick 
termination , differing from the reprefentations of Mr. Ikvelim. 
($0 The Medulla, and blaze with the manner of (hortning and 
lengthening, explained by the third figure > not feen the 2 2d. but 
the 23d. The bignefs of the Nucleus and Head through a Tele- 
fcope, compared with the top of a Tower. ( 4J The place it 
then appeared in. Why the motion was not more exactly obferved. 
Its blaze ftill not oppofite to the Sun. The 24th. not feen,nor 25th. 
('$. ) though the Sky clear by reafon of the height of Vapors. How 
they do lengthen the Crepufeulum. Why Phyfical Remarks only 
w ere made. (6.) Publilhed in order to underftand Obje&ions,and 
propound pertinent Queries. Some Obfervations, Notes, Queries, 
e^c. concerning the Comets in 1664. and 1665. here. Collected 
out of feveral fcattered Papers and Lectures of them formerly read 
here imperfect. Queries of its fubftance, magnitude, denfity, muta- 
bility, difTolutioa, fluidity, gravity, light, figure, motion bended or 
ftrai^ht, Cf r ) with equal or unequal velocity, in the Atmofphere or 
/Ether, above or below the Moon. Whether it wafts, or Ms to re- 
turn. The Star of a compacted light ( 8.) varied pofTibly from po- 
rtion, partly from real change, Tail tranfparent , Bodyfuppofed 
more denfe, fide toward the Sun evenly derin'd, Encompafled with 
a fluid yielding to motion,but diffolving its parts. Its light from its- 
felf. (9.) Its Nucleus fuppofed denfe poflibly as the middle part of 
the Earth, o£ which fome conje&ures. DhTolved by the /Ether as 
in our Atmofphere. (10.) Argument for theloofenefs of. the cen- 
tral parts of the Earth from the variation of magnetical direction. 
(11.) The Nucleus of Comets poffibly the fame. Internal motion 
may weaken gravitation. Parts feparated may be agitated by the 
gravitation of the ©. Tail made not fo much by the particles rece- 
ding as the Stars approaching the Sun. (12.) Howthe Comet 
may firft lofe its Orb in. the Univerfe, and paffing through the 

A3 fpheres- 



SYNOPSIS. 

fpheres of A6tivity of fevtral central bodies is deflected and attra- 
cted by them , and the Blaze raifed to a prodigious length. 
Ci3.)The bodies being attra&ed by fome gravity,Blaze expelled by 
levity, explained by fmoke , and fteams. Somewhat for pofitive 
levity. (14.) A digreffion concerning the method of Specula- 
ting the great and firft principles of the Univerfe. The Coma and 
Blaze like fmoke or flames. ("15.J) Shining particles a mining 
point, not a line of light. Gonfiderations and Experiments about 
the ways light is augmented by, as by fwift motion, adjacent 
dark medium, Flame explained. Why the Particles coalefce into 
a (beam. ( 1 £.J Enquiry about the magnitude and place of Co- 
mets. Many fuppofed them fublunary. fyebo and Kepler proved 
them cceleitial. How far we may rely upon Obfervations for Pa- 
rallax. Parallax and its effe&s defcribed. fi8J Tycbo fuppofed 

- the Comet of 1577. to move about the Sun. Kepler that of 1607. 
to move in a ftraight line v that of 166$. had no fenfiblc Paral- 
lax by what means it was found. (19.) Pvefraclion in this way 
varies little. Theory of Comets defective as to Parallax hitherto. 
Parallax not to be enquired from the Obfervations of feveral men. 
Errors creep in from the Prefs and the Graver , as in P. Gottignies 
Plates. f20.J Nothing to be concluded from Obfervations 
made by pcrfons in differing places for want of accurate Inftru- 
ntents, and Obfervations. (2 1.) Even the belt as Heyelius, Got- 
tignks, Petit, or Auzout err. Some reaion for this affertion. Moft 
of the reft altogether infignificant. (2?.) Want of Obfervers, 
Jnilraments, and Tables thecaufe. How thefe wants are to be 
fupplied. What the world expeclsfrom Mr. Hevelim. f 23.J And 
of how great ufe his Tables and Projections made by them will 
be. Parallax from diurnal motion failing. ( 2 4.J Other Parallaxes 
arifing from other hypothefes of the proper motions either of the 
Earth, or Comet, or both together confidered arife to a certainty. 
(2 5.J Others depending upon other fuppofitions define nothing of 
the magnitude or difiance of Comets. The inconvenience offy- 
cho's, and alfo of Kepler's Hypothefes explained. A third way I have 
taken. What confequences follow from it, (26.) As that it moves 
in a Circle that comes within the Earth Orb in ft, and without 
# Orb in «r, a fextant in 130 days, &c. This not relied on , be- 
caafe there may be other hypothefes to folve the phenomena > as 
that the Earth is unmoved,and the Comet moved in a Circle,whofe 
convex fide is toward the Earth. (27.) This hypothefis explained 
by thefixth figure. (2%.) The diftance and bignefs of the Circle 
of the Comet undeterminable this way without a diurnal parallax, 

fines the appearances may befolved by Circles of any bignefs, pro- 
v£d by. the eighth rigurc,(25>0 Allowing inequality of motion, or 

more 



SYNO P SIS. 

ntore compound curve lines, nothing can be determined. The cir- 
cular Orb it Teemed the raoft probable folves Kepler s acceleration, 
according to the increafeofa line of Tangents. (30.JA gravitation 
towards the Sun makes out the motion of the Comet, and Planets, 
and of the Blaze. The Blaze explained by experiment of $ diffol- 
ved in oyl of Virt. (3 1 OThis experiment and hypothefis farther ex- 
plained,and applied to explain the Blaze which is from thence bent, 
brighter on one fide than the other, not direel: from the Sun. 
( 32 J Cometical body and motion as old as the world , yet waft- 
ing in the /Ether i explained by fire. Diffolution by menfiruums. 
(3 3 JThence the proprieties of Comets con jedtured,and the fum of 
the foregoing difcourfe repeated, being the end of a Lecture. Re- 
courfe to Tycho Irak's Obfervation(340for making out theComets 
Orb. His fuppofing its motion unequal without reafon a {hift. Mr. 
Horrox hishypothefes in the ninth figure a product of chance, 
f 3.5O A difcourfe on it , and fome objections againft lycho's. 
(3$0 Kepler s hypothefis examined by thefe Obfervations of Ty* 
chos^ found the moft likely, but with fome alteration. Line of Tra- 
jedrion bent a little. Motion accelerated towards the Sun, retarded 
from it. ("370 Thefwifter and further off the Comet from the 
Sun, the lefs the bend,explained-by the tenth figure. ( 3 80The way 
of enquiring parallax by Telefcopes, (39.) further explained. A 
fecond way by two Obfervers in diftant places propounded. The 
third way of Sir ChrWren his Majefties Surveyor-General/ 4Q.J|Set 
down and demonftrated by a Geometrical Problem. (41. J How 
exactly all thofe Obfervations he had were made out by it,together 
with his own Schemes 5 both which I had in the beginning of Feb. 
ifd*. (42 Some other Papers about Comets added ., being re-r 
flections on Mr. Vefcartes and Kepler's hypothefes, from particular 
tracings of theComets of 1664. and 1665. A Scheme of the later 
Obfervations of that of 1664. added, and fome reflections, being 
all the papers couldbe found about thofe Comets. (43, 44O Ani- 
madverfions on this of April laft.Why the former- conjectures were 
adhered to concerning the light of Comets, f 45.) Several forts of 
mining bodies enumerated. (\6 ) To which the light of the Co- 
met feems to have moft affinity, and how produced. ( 47 *) Fur- 
ther defcribed and explained. (48.) The reafon of its parabolick 
figure demonft rated from the proprieties of motion from or toward 
a gravitating body,; as the Sum (49.J Concerning the wafting 
and lafting of the Cometical body. The bignefs and nature of the 
Particles that compofe. the Blaze. (50.) Some difficulties in this 
fuppofition concerning the action of the iEther in levitation and 
afcent, diffolution, (hining, &c. cleared and explained by Experi- 
ments. ( 5 j, 52, 53 But would have been further examined by;, 

Obi- 



SYNOPSIS. 

Obfervation if there had been opportunity. (54.3 That thefe aflertions a- 
bout the light of Comets may not feem too paradoxical, fome further Consi- 
derations and Obfervations about light are added , and fome new ways pro- 
pounded. OM^O Mr « Boy It's Memorial concerning a Phofphoros, writ- 
ten for his own ufe, inferted •, in which he firft names the Author of it, and 
defcribes his Apparatus, (57> *8.} Then the obfervables. 1. ~wo fpoon- 
fuls of matter enlighten a large glafs fphere. 2. A little enlightens a large 
Cylinder. 3. Liquor fhaken had a fmoke and flafht. 4. A dry fubftaace af- 
firmed to have continued mining 2 years, flamed; C$9.3 5. Someduftof 
this on a Carpet twinckled like Stars. Writing on paper with it fhin'd, and 
fmelt of Sulphur andOrions. (60.3 7. The hand on which it was rubbed, 
fhin'd, but felt no heat, (61.3 It fired Gun- powder firft warm'd. C62J) And 
white paper held over coals.Other tryal propounded,butrefufed.C&$.3some 
Experiments made on the Phofphoros Baldmnl in vacvo>and in the open air. 
0*0 Preferved in Vacuo, but deftroyed in Air. (6$, 66.) Monfieur Galln\ 
Letter to Monfieur Caffini, acquainting him with his Apparatus for obfefving 
$ in©. (^67,68.3 His Gbfervation of four fpots in . (69.3 The particu- 
lars obferved. (70. 71, 72.3 Monfieur CafflnPs Reflections on thefe Obferva- 
tions. (73, 74.3 Mr. Hallfs Letter to Sir Jonas M>or?,containing an account 
of his Obfervations of £ Tub file, three Southern Stars. The two Nubecula, 
& c * (.7$->1^77-) Mr « Caj/tnfs farther difcovcries about the diurnal motion* 
and feveral new appearances in %. £78,79, 80.3 

A fecond Difcburfe called Microfcopium , or fome new difcoveries with 
Microfcopes, in a Letter of Mr. Leemvenboec^. QBi. 82.3 A confirmation of 
fome of them by Obfervations here. (83.3 Mr. Leeuwenhos^s fecond Let- 
ter, containing Obfervations of the Globules of Blood, Milk, Flegm, Gums 
firft diffolved, then precipitated out of the Spirit of Wine 5 Eels a thoufand 
rimes thinner than a hair. Oh 8$, 86, 87, 88, 89.3 The ways how thefe 
difcoveries were made here, i* By holding the liquor in fmall pipes , how 
fiird, how made. The Lamp, Pipe, Oyl, Manner, Materials for making them 
defcribed. (89, 90.3 Mufcovy-glafs ufed inftead of thefe Pipes , and how 
the Microfcope was fitted for this purpofe. (91.) What light convenient. 
Surfaces of bodies not perfectly fluid apt to delude an Obferver, (92.3 Plates 
removing that deluding caufe, and what farther ufe of them. (93O How to 
find the figupe^nd texture of Animal and Vegetable parts. Inflance in a li- 
gament of Beef. C94.3 The figure of Mufcles hinted,. and an inftrument 
ft retching them before the Glafs defcribed. ("95.3 A defcription of the Mi- 
croscopes ufed, 1, Of the fingle Microfcope, and its advantages anddiffk 
culties. Q96.) another fortmore eafie defcribed, and the ways how to make 
and ufe it explained. (97.3 Caufes that vary the diftance ofobjefts from 
the Globule. The ufe of Selenites and Looking- glafs- plates, for holding the 
liquor. A Microfcope of one fingle rerefra&ion.(98.)The only inconvenience 
of rhem hinted, how prevented by double Microfcopes. Where thefe are 
made. ( 99 A The double Microfcope, and its parts, ufes, and advantages 
defcribed. (100.3 The benefit of a Hark Room, and appropriated lights. 
And a digreifion in anfwer to P. cberubints Accufation. (101.3 Some Obfer- 
vations made with this Microfcope hinted. Animalcules in the fteeping of 
other Grains befides Pepper. Their fmallnefs efti mated, and compared to a 
Whale. Mufcular fabrick hinted. Milk, Blood, Fat, Sugar, Alluai, &c. view- 
ed. (102, 103.3 Mr.Toung's Letter of one who trying to cure a Colick by lea- 
den Pills, dipt one into his Lungs ; grievous fymptoms enfue. ("io§. ) Helps 
-of skilful Phyficians in vain attempted, and particularly of Dr. Mayow, of fuf- 
pending with the head downward-,though in the interim he married and had 
Children, yet it kiU'dhim. (106, 107.3 H ' s body differed, and remarkables 
taken notice of 3 and their caufes explained by Mr. Toung,(Jrom 1 07. to 1 1 2.3 

COME- 





COME 

Remarks about Comets. 

j N Saturday morning, April 21.1677. 
I firft faw the Comet , of which I 
had been advertifed the day before. 
It appeared in the Sign Taurus , be- 
tween the bafe of the Triangle, and 
the unformed Stars in the Cloud of 
Arks, dignified by P. Par dies, with 
the figure of the Flower-de-luce; 
The head of it was in a right line, with the heart of 
Cajjiopea, and Alamak^ or the South foot of Andromeda, 
and as near as I could Judge" by my naked eye (^having 
no Inftrument or help by me) it was £ of the diftance 
between the feet and the Girdle of Andromeda^ diftant 
from the (aid Alamah^ towards the South. 

Its tail fometirnes as the Air was clearer and darker* 
extended about three quarters of its diftance from the 
aforefaid Alamah^ and pointed dire&ly at the Star in the 
nofe of CaJJiopea of the fourth Magnitude , and conie- 
quently the head of the Comet pointed not dire&ly at 
the Sun (the Sun then being about the eleventh degree 
of Taurus) but rather towards the fourteenth degree of 
the fame Sign. Its appearance was very imall and (lender, 
and as people commonly ghefied,about two yards long* 
and the head about the bignefs of a. Star of the firft 
magnitude, but of a much fainter and duller light. Its 
blaze about three o'the clock feemed to rife ftraight up- 

B ward 



U1 

ward, before that about half an hour after two it lean- 
ed a little Eaftwards, or towards the right hand , and 
after three, as it rofe higher , inclined towards the left 
fide or Weftwards. The head to the naked eye was 
brighter than the blaze, and (eemed to be fomewhat 
bigger than that part of it which immediately joyn'd ta 
the head 3 butthofe parts of it which were farther di- 
ftant, were of a much greater breadth 5 fpreading wi- 
der and wider , as they were more remote from the 
head, and in the fame proportion alfo growing fainter 
and fainter in their light , efpecially towards the out- 
fides 1 but the middle parts or medulla, appear'd much 
longer, and the brightnefs much greater , which made 
Ae whole blaze to feem to taper, or be pointed towards 
the top. 

The length of the Blaze appeared fometimes fllor- 
ter.> and fometimes longer > by feveral viciffitudes y and: 
as the day-break, or dawning increafed , (b the Blaze 
fliortened, and efpecially towards the fides near the top, 
and fhortly after before the Sun role^difappeared. 

But notwithftanding this fhortning and lengthening; 
of the Blaze, I could not perceive any kind of motion in 
the parts of it, fuch as is obfervable in flatue, (moke, 
or other (teams rifing from a burning or hot body : but 
fche fame parts of the Blaze (eemed to appear and di(ap- 
pear in their proper places as if they had been (ixed^and 
afolidbody. 

The firft Figure Lhave here annexed* will with (bme 
ftiort explications, reprefent the appearance of it to the 
eye, more plainly than by a multitude of words, with- 
out it 'tis poffible to cxprefs. 

A, reprefents the head of the Comet, the middle of 
which appeared brighter than any other part*, about 
which was a hazy light fomewhat like the fhiningof a 
Star through a thin cloud > the lower part of which was 
pretty round and defined. B, the neck of it y which 
feemed to the naked eye of lefs Diameter, and left 
bright thaathe head:, but through a fix-foot glafs, as I 
' (hall. 



CO 

(hall mention by and by, it appeared bigger , thought 
not fo bright. The middle of this was very bright , and 
feemed to iffue from the Nucleus or Star tn the middle 
of the head. C, the brufhy parts which were fainter 
and paler towards the fides , efpecially nearer the top 3 
which made the whole feem to taper and refemble the 
Figure here expreft : Obferving it with Telefcopes ("one 
of which was fifteen foot , and the other fix foot long) 
I found the (hape of it much like this, which I have re* 
prefented in the fecond Figure. 

It had a pretty bright Star (if I may fo call it) near 
the middle of the head, feeming much about the bright- 
nefsof 1? when near the Horizon, and was about 25 
feconds in Diameter, as is reprefented by A , not per- 
fectly defined, but hazy 3 the cloudy part or beard of 
the body encompafiing icon all fides : but that part of 
the Coma. B, which was next towards the Sun, was the 
narrowed: nor was this Coma well defined , but the 
outward parts of it were fainter and fainter. However 
they were regularly enough terminated to make the out- 
wardmoft bounds of it of a kind of Parabolical figure £ 
the moft bent part of which was towards the, Sun, 
and moft defined : And the bright Star of it was, as I 
have exprefted it about four of its Diameters di- 
ftant from the faid parabolical limb. The light parts of 
the ambient Cloud Teemed to fpread gradually towards 
that fide of it, which was oppofite to the Sun 3 but thofe 
which were next the middle were the brighteft : and al- 
ways as they were farther and farther from the Star in 
the head, the fainter and paler they were, 

I ^ould not obferve any reprefentations like thofe 
which are given us by Mr. Hevdius, in his Cometogra- 
phy, neither in the Head, nor the Blaze , no more than 
I could in thofe which appeared in the years 1664. and 
1665. as may be eafily taken notice of by comparing 
thefe which I have here delineated with thofe. 

The middle part of the Blaze CC, 'which afcended 
from the Star in the middle, feemed the brighteft, and 

* 2 Of 



[43 
el: this medulla or ftem, thole parts were brighteft which 
wereneareft fituated to the faid Star. The fides of it 
grew fainter and fainter, as they were farther from the 
head ^ and though they had brightnefs enough to make 
them appear in a dark and clear sky, yet the dawning 
quickly made them vanifh , and dilappear , as did any 
hazinefs of the Sky : and according as the light increa- 
fed, fo was the Blaze dim inHhed, after the order of 
the tapering prickt lines expreft in the third Figure by 
a aa, b b b, c c c, d d d, &c. and even in a clear and 
dark Sky, towards the farther end of the Blaze they of- 
ten difappeared for fome (hort (pace of time , though 
the middle or ftem continued 5 and fo it caufed the re- 
maining appearance to refemble the figure of a very 
fiender birchen whisk or brufri, much like that reprefen- 
ted in the firft figure. 

The 22. from half an hour after two, till half an hour 
after three, the North-eaft part of the Heavens to me 
was cloudy, and the Sky between the Clouds was ha- 
zy, and the dawning (truck much higher than the day 
before, fo that I could not find it. 

The 25. withfeveral friends I obferved it again , the 
Sky being clear, and confirmed my felf in ail my for- 
mer obfervations , taking again diligent notice of all 
circumftances remarkable, both with my naked eye, and 
with Perfpe&ive-glalTes. And T had this morning a very 
notable observation in order to meafure the bignefs of 
the Star and its Coma, which encompafied it, by compa- 
ring it with fomewhat fixt : for fome few minutes be- 
fore three of the Clock the head of it paft juft behind 
the type or top-poft of a tower not f*ir diftant, and was 
quite eciipfed by it - y and as fbon as it appeared to have 
paft it, feeming yet contiguous , T obferved it with my 
fix foot Telefcope, and found the Coma or whole head 
to appear^full as big as the (aid type or timber poft, and 
the Nucleus or Star in the middle of it, to be very near 
of the iamebignefs of the iron ipindle, upon which the 
weather-cock was fixt. Whence upon examining the 

4 bignefs 



£53 

bignefsof the faid parts, fince by an accurate Inftru- 
ment I judge the head or Coma was about 4| minutes 
in Diameter, and the Nucleus or Star about 2 5 feconds. 
I took notice this morning that it had much altered the 
pofition in the Heavens, which it had upon Saturday 
morning, and that the Blaze of it was very much de- 
flected out of the line it appeared in the laft time. And 
with a finall crofsftaff, taking the diftance of it from 
Alamak, and from Gtnih , in the left fide of Perfem. I 
judged it to be in the mid-way between the Flower-de- 
luce aforefaid, and Algols or the head of Medufa, that 
is, about 14 degrees of tf, and 17 degrees of Nor- 
thern Latitude : fo that I judged its motion almoft Eaflr* 
but a little defle&ing South. I was not much (olicitous 
of making obfervations of its true place, as not de- 
signing my prefent enquiry to be for what kind of moti- 
on it had, conceiving its motion to be towards the Sun, 
and fo of very little duration : and expefting to hear 
an account of that from other places, andlperfons that 
were better furniihed with Inftruments and convenien- 
ces for obfervations of that kind than I was then. 

The Blaze extended it felf in a right line towards the 
Star in the right thigh of Cajfiopea, being a Star of the 
third magnitude. Its length at firft was about 7 or 8 
degrees , and did fometimes* feem longer , fometimes 
fhorter, as I noted before, without feeming to have any 
other motion in it but the Diurnal motion,the fame with 
the fixt Stars on Earth. Whence I collected , that the 
head of it pointed towards the feventeenth degree of 
T^r^r in the Ecliptick, though the Sun at that time 
was about the thirteenth degree of the fame Sign. 

The 24. with feveral others , I attended the appea- 
rance of it, but the. Sky in that part of the Heavens was 
overrcaft with Clouds. 

The 25. I expe&ed to have a farther Obfervation of 
it from half an hour after two,, till a quarter after four 5 
but notwithftanding the South- eafterly wind i and the 
clarifying quality of the air, which before half an hour 

■ B 3 V afi:et: 



en 

after three had partly carried off, and partly diflblved 
the black thick Clouds (with which the North-eaft 
parts of this Horizon was over-call: about three of the 
Clock) and left that part of the Heavens where the Co- 
met ftiould have appeared clear , and without Clouds. 
Yet the air being very high and heavy , as the Barome- 
ter (hewed, the upper parts of it were fo rilled with the 
dawning light of the morning, that neither the Blaze 
head or Star of the Comet appeared to me in the leaft : 
nor had I any fight of itfince. 

The like appearance of the great height of vapors in 
the air, when it is very heavy, I have often taken no- 
tice of, and have obierved , that the twy-light and 
dawning between the night, and appearing of the Sun 
is very much altered thereby. And that a heavy air, 
when the vapors are raifed high, will make the length 
of them much greater,and confequently the night (hort- 
er. And a light air, on the contrary, fhortning them, 
doth lengthen the night. 

Thefe were the moft remarkable circumftarices I took 
notice of in this Comet, being altogether Phyfical, and 
defigned only for enquirng into the confutation of thefe 
wonderful bodies : the accounts and opinions we have 
hitherto had of them of that kind , being very unfatif- 
fa&ory. Though other Oblervations, to wit, Mathe- 
matical, of the way, celerity, and magnitude of Comets 
have been profecuted with very much care, and great 
skill 5 fuch as thofe of the noble Tycho, and the learned 
and diligent Hevehus, infcmuch that I could not expeft 
to have better 5 yet as to Phyfical remarks , I wanted 
much information to be able to fetisfie many difficulties 
that occurr'd to my thoughts , upon enquiry into the 
particular natures of them. I did therefore, as I de- 
figned, employ all the time I could get of obferving this 
Comet, in takrhg notice of fuch circumftances as I 
judged would be pertinent to refolve any of thofe Que- 
ries I had formerly made, in order to find out the nature 
of Comets in general, And though the little oppor- 
tune- 



17 J 
tunity I now had, and the disadvantageous appearance 
of this lad were very fhort of giving me that fatij&ai. 
on in manyparticulaxs which I wifti'd for,and expe&ed at 
firft, yet fince they may poffibly ferve for hints to others 
that may hereafter have better oportunity than I , and 
that I might underftarad what material objections could 
be made by observers from preceding Comets, and that 
they might for the future more diligently take notice 
of what from thefe queries and hints may be judged fig- 
nificant tothisdefign, fuch as they are I have here pub- 
lifhed as I had done formerly by my Leftures in '-Gr«- 
jto-Colledge,thoFe which I had made of thofe in 1664, 
and 1665. 

Now before I come to make reflexions upon theft re- 
marks, I thought it might Hot be improper to add fome 
few of thofe things concerning thofe two former Co- 
mets obferved by me in the fiid years. I fay, fome few^ 
becaufeit would be needlefs to fet down all , efpecially 
fuch of mine as do agree with others fince publifed^ 
I did therefore foon after I had feen the firft Comet, to 
wit, December 23. 1664. propound to my felf certain 
Queries neceffary to be anfwered ,,in order to find out 
a true theory of them ( and directed my ©bfervations 
accordingly 3 and they were thefe. 

Of what fubftanceits body, beard; and blaze is > and! 
next, of what magnitude each of thofe parts, appear^ 
and of what real magnitude they are>- 

Other Queries were concerning its denfity and rari- 
ty, its mutability or immutability 5 that is, whether it 
diilblved apfwafted or not ? whether it were fluid or 
folid > whether it participated of gravity or levity > 

Whence it had its light, colour, &t\ 

What was the figure of the Star 5 Radiati©n,Biaze^« 

Whether the Blaze were always oppofite to the Sun, 
or deflefted > whether ftraight or bended, &c. 

What kind of motion it was carried with> whether 
m a ftraight or bended line > and if bended, whether 
in a circular 0^ otherxurve, as elliptical or other com- 
pound 



[8] 
pounded line, whether the convex or concave fide of 
that curve were turned towards the earth? Whether in 
any of thofe lines it moved equal or unequal fpaces in 
equal times } 

Through what parts of the univcrfe it moved , and 
how far diftant it was at feveral times? Whether in the 
lower Regions near the Earth in the Atmofphere, or 
near it, or in the Heavens, or fluid iEther, with which 
thefpaceof the Heavens is filled? Whether above or 
below the Moon, &c. 

Whether it wafts, and is difperfed andconfumed? or 
whether it lafts and endures for a longer time ? If it 
lafts, Whether it ever appears again , being moved in 
a circle 5 or be carried clear away, and never appear a- 
gain, being moved in a ftraight or paraboloeidical line ? 
Whether it be colle&ed or generated when it iirft ap- 
pears ? and diffipated or deftroyed when it difap- 
pears$ or whether the feveral diftances of it do not 
make that appearance ? 

Whether it may not have fome fiich propriety, as the 
Star in Cete, whereby it may (hine and appear for a cer- 
tain period , and again lofe its light , and difappear 
by feveral viciffitudes ? and whether that may not 
give fome account of the appearance of fo many Comets 
about Arks? 

Firft, As concerning the matter or fubftance of the Nu- 
cleus Star or body,of the hazy (hining part encompafiing 
it, and of the Tail or Blaze : I fay, that by comparing 
all the circumftances that I was able to take notice of 
from the beginning to the end, I found that the Star in 
the head was of a very compafted and denfe light, and 
almoft equalled that of Saturn 5 though it were not like 
that confined by an equal limb : that there were fome 
parts dif tinguilhable in this body, fome having a bright- 
er, others a fainter light. That thefe parts did not 
continue the fame, but considerably varied,which might 
in part be caufed by the differing pofition of thofe parts 
which were feen before, from the fame feen afterwards, 

in 



E9] 

in refpeft of the eye , fituate on the furface of the 
Earth, moved one way , and the Comet moved ano- 
ther $ though I do not conceive it wholly aicribable to 
that, but partly alio to a real alteration of the parts of 
the Gomet. That I did very diligently watch to ob- 
ferve if it were poffible, when it pafs'd over any fiVd 
Star to find whether it were tranfparent 5 as I had fe- 
veral times obferved the tail of it to be even in its 
brighteft parts, but I had not the opportunity 5 but that 
I did feveral times oblerve the tail of it tranfparent, not 
only with the naked eye, but through a Telefcope : if 
at lead: the fixed Stars be above it , which I think few 
doubt, that the light diminiftYd by degrees towards 
the extremes of the hazy part encompaffing it} and yet 
the extfflfemes of it as to that part of it which refpe- 
&ed the Sun , feemed pretty evenly and fmoothly de- 
fined, efpecially through a Telefcope : From all which 
remarks, and from the velocity of its motion, I con- 
jecture it to be made up of folid matter, not fluid $ that 
the body of it efpecially , is considerably denfe, but 
that the hazinefs or Coma about it is much more rarified, 
and the tail thereof is moft of all. That this body is en- 
compaffed with a body moft fluid , and eaftly permea- 
ble, and which doth with very little refiftance give 
way to the motion of it, or any other body through it, 
that it doth eafily admit at leaft (if not a&ually take in- 
to it felf; the parts of this body, Coma^ and Blaze. I 
fay, admit at leaft, (though there may be many realons 
alledged that it doth actually prey updn , and diiTolve 
thofe parts into it felf, as I (hall (hew by and by) be- 
caufethat we find that the extreme parts do extend but 
to fiich a diftance , and beyond that there is no appea- 
rance of light , and that the light is from it felf, and 
not produced by refra&ion or reflexion of the beams of 
the Sun,I (hall (hew reafons by and by. And confequent- 
ly, where there is moft light appears,there are the great- 
eft number , and there is the greateft denfity of the 
Cometical parts. The middle of the body may be as 

C denfe 



denfe as the body of the earthy and I have not obfer- 
ved my felf, nor met with any body elfe that hath taken 
notice of any thing to the contrary : If I could have 
feen any Comet to have covered any Star in its way i it 
would have afforded a very circumftantial information, 
efpecially if for this purpofe it had been taken notice 
of withagoodTelefcope. What the denfity of thein- 
nermoft parts of this Earth we live on is,*noneknows5 
for though we find the parts on which we tread to be 
very compact, and though by the induftry of Miners it 
hath been proved fo alfo to the depth of many hundred 
foot, as Georgim Agricola relates : and though it hath 
been found fo even to a greater depth by the foundings 
of the bottom of the Sea, yet none can bring an unde- 
niable proof that the fame is fofolidto 2 5mi*fc deeps 
much lefs that it is fb to the center : if therefore the ex- 
ternal {hell of this Globe were broken , and removed, 
'tis not impoffible but that the middle parts thereof 
may be of the fame nature with the middle parts of the 
Comets body 5 and that thofe parts (were the fuperfi- 
cial parts or fhell removed) might , like thefe of Co- 
mets expand themfelves into the encompaffing iEther. 
Nay we find , that notwithstanding the compa&ed- 
nefs of the fuperficial parts of this Earth, yet the iEther 
is able to take up into it felf vafi: quantities of them, and 
to keep them fufpended , fome of them, even to the 
height of many miles, if any argument may be drawn 
from the height or length of the dawning or Crcpufcu- 
km 5 and this , notwithstanding the attra&ion of the 
Earth in its perfect vigor , or the gravitation of thefe 
parts thus taken up , or their endeavour towards the 
center of the Earth. How much more freely then 
might we imagine the ^encompaffing iEtber to prey up- 
on, and take up into it felf the internal parts, if they 
were of aloofe and pervious texture, and almoft in a 
flate of fluidity, like a heap of Sand, or a vcflel of Ala- 
bafter-duft in boyling, and were not fo firmly united 
by the bonds of gravity , and the vinculum of petrifa- 

ctioo, 



&ion, as we find the fuperficial parts of the earth now 
are.There is one argument to prove to us,that there may 
be fuch aloofenefs of the internal parts of the earth,and 
that is that the magnetical virtue varies, which virtue 
without controverfie diffufed through the whole body 
of the Earth, and which hath a relation to the whole 
Globe, and to every magnetical part thereof. For by 
obfervation 'tis found, that the magnetical virtue afts 
upon a needle without it, as the magnetical virtue of 
a round Loadftone doth on a Needle applied without 
that, which, as I may elfewhere fhew , hath a refpeft to 
the center of the ftone differing from all the refpe&s 
that Authors have hitherto afcribed to it 3 even of Gil- 
bert^ Kepler, Kircher , Defcartes , and our Country- 
man Mr. Bond, who I think was the firft man that 
endeavoured to reduce the variations obferved by 
Wright, Gelli brand, Cojier, Sec. into a Theory and calcu- 
lation. Now this magnetical virtue, (which may be cal- 
led one emanation of the Anima mundi, as gravity may 
be called another^) being diffufed through every part of 
it , and feeming to be , as it were Tot* in toto & 
tota in qualibet parte, and to be more fpiritual , and 
to ad more according to Magical and Myftical Laws 
than Light, Sound, or the like, it giving to every mag- 
netical body, and every piece of it , though infinitely 
divided , the fame proprieties it hath it felf 3 Thia 
magnetical virtue, I fay, having fuch a relation, and be- 
ing forced thus to vary, 'tis very .probable that the in- 
ternal parts to whichit hath a refpeel: , have a variation 
likewife, and confequently , that thefe internal -parts 
which are fuppofed generally very denfe, compact, and 
very clofely and folidly united, may be notwithstanding 
moreloofe, and ununited, and movable from certain 
caufes. 

To proceed therefore, I fay, that it feems very pro- 
bable to me,tbat the body of Comets may be of the fame 
nature and conftitution with that of the internal parts 
of the Earth, that thefe parts may , by the help of the 

C 2 JEther, 



E> ] 

iEther, be fo agitated and blended together, as to make 
them work upon, and diflblve each other in the fame 
manner, as we have often had examples of fome of 
the parts of the Earth 5 a late inftance of which was at 
Mongibelox Mtna in Sicily , where the Fire continued 
for a long time, and produced very considerable effects. 
That this internal agitation may confound the gravita- 
ting principle, and fo leave the parts in a greater free- 
dom to be diffolved by the encompaffing JEther, which, 
is the agent that lets the other two at work to deftroy. 
each other, that it may at length prey upon both , and. 
diffolve them both into it felfj. and confequently , not 
only the parts thus diffolved are elevated to a greater, 
diftance from the center of the Star or Nucleus , or the 
fuperficies of it, whofe gravitating or attractive princi- 
ple is much deftroyed , the Coma being in this Comet 
four or ftvc Diameters of the Star or Nucleus : but ha- 
ving given thofe parts leave thus far to ramble, the gra- 
vitating principle of another body more potent ads up-. 
on it, and makes thofe parts feem to recede from 
the center thereof, though really they are but as it; 
were, left behind the body of the Star, which is more, 
powerfully attracted than the minuter fteaming parts : 
for, I fuppofe the gravitating power of the Sun in the 
center of this part of the Heaven in which we are 5 hath 
an attractive power upon all the bodies of the Planets, 
and of the Earth that move about it, and that each of 
thofe again have a refpect anfwerable, whereby they, 
may be (aid to attrafttheSun in the fame manner as the 
Load-ftone hath to Iron,and the Iron hath to the Load- 
ftone. I conceive alfo that this attractive virtue may act " 
like wife upon feveral other bodies that come within the 
center of its fpherc of activity, though 'tis not improba- 
ble alio but that as on fome bodies it may have no effect 
at all, no more than the Load-ftone which ads on Iron, 
hath upon a bar of Tin, Lead, Glafs, Wood, &c. fo on 
other bodies, it may have a clean contrary effect , that 
is, of protrufion, thruiting off, or driving away , as 

we 



[13] 
we find one Pole of the Magnet doth the end of a 
Needle touched on the oppofite part & whence it is , I 
conceive, that the parts of the body of this Comet (be- 
ing confounded or jumbled, as 'twere together , and 
fo the gravitating principle deftroyedj become of 
other natures than they were before , and fo the bo- 
dy may ceafe to maintain its place in the Univerfe, 
where, firft it was placed. Whence inftead of continu- 
ing to move round fome central body, whether Sun or 
Planet, as it did whilft it maintained it felf entire, and 
fo had its magnetical quality (as I may fo call it) uncon- 
founded , it now leaves that circular way and by its 
motion -(which always tends to a ftraight line, and 
would be fo were it not bended into a curve by the at- 
tractive virtue of the central body) it flies away from 
its former center by the Tangent line to the laft place, 
where it was before this confufion was caufed in the 
body of it. In this line ('tis probable ) it paiTes from 
one part of the Heavens to another , and fo paiTes 
through the fpheres of the a&ivity of multitudes of 
central bodies 5 in the palling through which fpheres, 
'tis not improbable that thofe parts which by their diiTo- 
lution are made of a nature differing from the body in 
the center, are rather expelled from, than attrafted to- 
wards it 5 and fo being by this didolution rarified, and 
loofened from the middle, and by their a&ing upon one 
another, and dilTolutionof the Mther made of another 
nature, after they have every way difperfed themfelves 
to a confiderahle diftance from their proper body, are, 
converted and driven in a way almoft oppofite to that 
expelling body , and fo continue to be driven away 
to fuch a vaft diftance, as to make out that prodigious 
length of the tail or Blaze of fome Comets (fuch as 
was that of 161 8. which 5 as Kepkr reports, was exten-. 
ded to 70 degrees from the body or head of it) till at 
laft they are diilolved alfo , and commixed with the. 
iEther within them. So that though I fuppofe the at* 
tractive power of the Sun, or other central body may 

C 5 draw 



C 14 1 

A 4 aw the body towards it, and fo bend the motion of 
the Comet from the ftreight line, in which it tends, in- 
to a kind of curve, whole concave part is towards the 
Sun, by reafon that there are fome central parts of it, 
which are not yet deftroyed, and fo retain fome what of 
its gravitating principle: yet I conceive that all thofe 
parts of the Comet which are thus wrought upon by 
the other, and changed into another ftate, and are ve- 
ry much rarified, and produce light, are of a clean con- 
trary nature, and recede from the center of the Sun : 
much after the fame manner as we find any combuftible 
body with us 5 as Coal, &c where we find that the 
body of the Coal, before it be refolv'd into fmoke , is 
a very denfe, and very heavy body , and tends to the 
center of the earth 3 but the parts thereof agitated by 
the Air and iEther into fteams and fmoke, and thofe yet 
farther diflblved into flame, do tend upwards, and from 
the center of the earth. Now though one caufe of 
the recefs of flame from the center of the Earth be 
the gravity of the ambient Air. Yet 'tis not impoffible, 
but that there may be fomewhat alfo of pofitive levi- 
ty conjoyned therewith. Moft certain it is, that there 
muft be a tendency of receding, as well as a tendency 
of approaching the center of the Earth , and other at- 
tracting body. And there may be much faid for the 
fuppofition, that the recefs of the pureft iEther , from 
the center, is the caufe of the motion of the groffer 
iEther, and of all other bodies towards it, though 
there are alfo very confiderable arguments againft 
it. But this difcourfe is not my prefent bufinefs, though 
it may hereafter be the fubject of a Lecture in this places 
for upon it do depend fome of the greateft operations 
in the univerfe. And as in the Hiftory of the Creation, 
we have an account of the production of light , imme- 
diately after the making of matter, which is a motion 
of recefs from the center of the ihining body. Next 
that, a Firmament which divided between the waters or 
the fluids of the one, and the fluids of another part of 

the 



C*5 3 
the world. And in the third place, the collections of 
particular fluids to one center, as the center of the 
Earth : and laftly, out of that collection of fluids ap- 
peared the dry and folid land. So I conceive the moft 
proper way of fpeculating on thefe great produftions 
of the omnipotent Creator, may be to begin with the 
confideration of light, or the motion of recefs from the 
center of a body. Next, with the confideration of 
thecaufe of the feparating of fluid from fluid , as J£- 
ther from ^ther, as I may fo call differing Others 3 be- 
caufe we have not yet diflina names in ufe , and the 
reafon of their conglobation, the iEther from the Air, 
the Air from the Water, the Water from Quickfilver 
Oyl, or other fluid. Thirdly, the caufe of the conglo- 
bating property of each of thefe fluids when fepara- 
ted , how they accept and embrace Homogenea, and 
reject or expel Heterogenea. Andfburthly , how they 
condenfe and fettle together, and produce a folid bo- 
dy : whence proceeds the confirmation of attraftion or 
gravitation, &c. But to digrefs no further - but con- 
clude this part of enquiry in fhort , I fuppofe the Nu- 
cleus or Star of the Comet may be much of the like na- 
ture with the central parts of the Earth, Moon, Mars, 
Jupter, Saturn, or other Planets , but much impaired 
in its attractive or gravitating power. 

Next, that the Coma or Hazy Cloud about it, may be 
of the nature of the Atmofphereor Air about the Earth, 
or the Smoke or fleams about a heated or burning body 
before they are quite kindled, converted into Flame, or 
diflolved into the ambient Air. 

Thirdly, that the Tail or Blaze is much of the nature 
o.f the parts of Flame, though with thofe differences I 
conceive, that the parts of thefe fleams are not fo clofe 
together, as are thofe of Smoke : nor doth the motion 
of them, though much fwifter upwards than that of our 
Flame, ferve to make them appear a fliining line$ but 
being at that diflance, they appear much flower to the 
eye, and fo difcontinue the appearance $ Whence every 

Chining; 



fhining particle appears only a ihining point, though in 
the parts of flame (where notwithftanding the motion 
be much flower, yet being nearer , and fo varying the 
pofitionto the eye much quicker) each of the (hilling 
parts makes an appearance of a line of light, and all of 
them palling pretty near together, make the appea- 
rance of a continued fluid flame 5 though that indeed 
be nothing but a great number of Angle parcels of the 
burning body, raifed up in the -particles' of Smoke. 
This will appear evident if we confider the appearan- 
ces eafily to be taken notice of in light : for 'tis obvi- 
ous from multitudes of experiments , that any fhining 
body, as a candle or brands end, being moved very 
quick, makes the fame impreffion on the eye, that a line 
of light doth (landing (till : And as obvious alfo that 
any very light body incompafled with a dark medium 
appears to the eye under an angle bigger than really it 
is, and a dark body encompafled with a light medium 
muchlefs. This any one may prefently find, if he make 
a fmall hole through a thin plate of metal , and holding 
it firft between the light and the eye , and fo feeing the 
light appear through it, and then placing it fo as there 
is nothing but darknefs appears through the faid hole, 
for he will plainly perceive that the fame hole will ap- 
pear much bigger in the former pofition than in the lat- 
ter. Upon this account indeed each of the ihining 
parts of the Gomet ieems to fill and occupy a much 
greater (pace than really it doth: and fo, as 'tis obfer- 
vable in the milky way, a great number of the(e fmall 
fhining bodies though difperfed at a pretty diftance one 
from another, yet by reafonof the imperceptiblenefs of 
each of them they all feem to coalefce into a ftream or 
Blaze of light, the brightnefs of which is yet farther 
augmented by a clear and unenlightened air, and by 
fucha part of the Heaven wherein there appears feweft 
of the Stars, whether they be greater orlelTer. 



To 



C n 3 

To the Query ,0/ 'what magnitude the Bod)., Command 
Blaze of Comets may ^.<?No anfwer can be given until an- 
other queftionbe firft anfwered, and that isJVhat is the 
place of Comet s^and what is their di fiance from the Earth £ 
It was the opinion of mod: Modern Writers before 
Tjicho Brake and Kepler (I know divers of the Antients 
thought otherwife) that Comets were fublunary Me- 
teors, drawn up into the higher Regions of the Air 5 
and there fet on fire, and fo continued burning till the 
Meteor were confumed , and as the matter increafed, 
or wafted , fo did the appearance of the Comet. But 
this noble Dane , and feveral others about that time 
found by accurate obfervations made, that its Parallax 
was le(s than that of the Moon ^ and confequently 5 
that it was farther diftant from the earth : that it muft 
be a body of another magnitude, and nature, than mod: 
before that time had imagined 5 and therefore that it 
ought to be otherwife thought of than the generality 
of mankind believed concerning it. Many had been 
the attempts of former Writers concerning them , to 
find out their parallax 3 and whether from their unac- 
curate inftruments, or from their lefs skill and diligence 
in ufing them , or from an imagination of the folidity, 
and impenetrability of the CoeleftiaJ Orbs, or from er- 
ror in their calculations,or from comparingObfervations 
made at diftant places, one or both whereof were un- 
accurate, or from a prepoffeflion of Tradition or com- 
mon Fame, or from what other caufe (bever it were is 
uncertain 5 but 'twas generally concluded by them, 
that all Comets were fublunary Meteors : and there 
are not even at this day wanting fome of the fame 
opinion, though for what reafon I know not. Twill be 
hard to convince fome of thefe, that the opinion they 
have hitherto received for good, is not fo, becaufe they 
will hardly give themfelves the trouble of examining 
ftri&ly into the matter : And tounderftand the nature 
of Parallaxes , and how fignificant they are in deter- 
mining the diftances of bodies from the furface of the 

D Earth 



t «* ] 

Earth, to certain degrees thereof 5 beyond which , by 
reafon of the imperfeclions in Inftruments, and Obser- 
vations, and the exceeding niceneis and curiofity necef- 
fary, they fignifie very little. It is not my prefent de- 
fign to explain what Parallax is , that I would fuppofe 
myReadertounderftand} otherwife there can be no 
reafon (hewn him to convince him that 'tis poffible to 
prove that this or that Comet was not nearer than fo 
many femidiameters of the Earth, nor farther off than 
fo many. There are then two ways, by which we may 
come tofome certainty of what diftance a Comet is$ and: 
thofe are, firft the Parallax of its Diurnal motion, or its 
Parallax caufed by the Diurnal motion of the Earth. And 
fecondly, the Parallax of its proper motion compared 
with the Periodick or Annual motion of the Earth. The 
firft of there may be obferved two ways 5 either by two 
Obfervers at parts of the Earth very far diftant from 
each other, but as near as may be under the fame Meri- 
dian : as fuppofe the one in London^ the other in St. He- 
lms } both confpiring in their oblerving of the place 
of the Comet amongft the fix'd Stars at the fame time. 
Or fecondly, by one Gbferver in the fame place, by ob- 
serving the place of it amongft the fix'd Stars, in its ri- 
fing or fetting, and in a greater, or if it may be, its 
greateft height: The noble Tycho by very accurate 
Obfervations of the Parallax , proves the Comet 
of 1577. to be above the Moon. Kepler by his 
own Obfervations proves that of 1607. at i ts begin- 
ning to be four times farther diftant^and I doubt not but 
lome may have been above forty times farther.But I do 
not yet find that any Obfervations have accurately de- 
termined that which is indeed the great help by which 
we are inabled to judge of the nature , and all the o- 
ther accidents and proprieties of Comets. The Arijle- 
telUn Pbilolophy for a long time prevailing, made the 
world believe themtobe nothing but Exhalations from 
the Earth, drawn up into the higher Regions of the Air. 
But Tjchoby his Obfervations of their Parallax, raifes 

them 



t 19 ] 
them out of that confinement, but yet he feems to place 
them in an Orb about the Sun. But Kepler frees them 
from that confinement , and affigns them the Univerfe 
to expatiate in. But none of all thefe do accurately 
prove the true diftance of them, their Parallax beine 
for the moft part fo very fmall, that I fear Inftruments 
with common lights will hardly reach them. But we 
muft expeft from future obfervations made with Tele- 
fcopical Inftruments to receive a certain Anfwerto this 
Query. Certain I am, that the Comet which began 
to appear mNovember 1664. and difappear'd in March 
following, was far removed beyond the diftance align- 
ed by Kepler. For by my own Obfervations divers 
times repeated , I could not find any fenfible Parallax 
though I endeavoured by a new method to make my 
Obfervations more accurate. Now though I had not 
the convenience of making ufe of a Quadrant, or any 
fuch Inftrument, to obferve its place when near the Ho- 
rizon, yet the way I took, would, I think, be as good 3 
which was this : With a very good fix foot Perfpedive- 
glafs or Telefcope, I obferved the place of the Comet, 
m refpeftof the adjacent fmall Stars, as foonas it ap- 
peared, and fo traced its way till it difappeared in the 
vapors of the Horizon : the like I did feveral other 
days fucceffively, taking notice by what degrees, in 
what times it made its progrefs, to fee whether by its 
Parallax, when near the Horizon, it would have been 
depreft below that line of its motion, which it kept, 
when at a greater height above it. But though I tried' 
this feveral times, yet I was not able to difcern that the 
Parallax of it caufcd either any fenfible bending of the 
line,or any fenfible inequality in its progrefs,by which I 
fhould have fooner found it,than by taking its altitudes 
with common Inftruments:though I confefs thefe Obfer- 
vations were made when the motion of the Comet was 
flow, and confequently , when in probability it was 
far diftant from the earth. To me there feems no doubt 
but that it was along way removed above the Moon 

E> 2 when 



when I made theft Obfervations : for had it beenof an 
equal diftance with that they allow the Moon, it muft 
this way have manifefted a very fenfible Parallax of di- 
vers minutes : but whereas I could not certainly diftin- 
guifh any fenfible at all , it muft be many times higher 
than the Moon. Now that this way is abundantly to 
he preferred before an Obfervation made with a Qua* 
drant for the taking of its altitude , is pretty evident 5 
becaufe, by this, means the greateft part of the irregu- 
larity, caufed by the refraction or inflection of the Air' 
is removed j for by this means, though the Parallax be 
very large, yet the refraction or inflection of the Air* 
will not amount to many feconds, both the objects be- 
ing almoft equally raifedby refraction,, efpecially when 
5 or 10 degrees high 5 nearer than which. the fmall Stars 
Yanifhed out of fight by the thicknefs of our air. It 
follows therefore that a Semidiameter of the Earth 
muft be a very inconfiderable meafure in its diftance. 

This part therefore of the Theory of Comets, hatb 
been much defective hitherto. If we enquire the 
Parallax of them from the Obfervation of divers men 
made in differing places, we {hall find them fo differing* 
one from another, that there is* great reafon to fufpect; 
them all: Nay, not only fb, but in this Comet of 1 664; 
by comparing two Tables or Charts of the Stars, and 
Compilations of that part of the Heavens , through 
which the Comet, paft , on which was alfo markt out 
its way and place from day today, both of them Prin- 
ted from Copper Plates, I find that ftrange errors and 
miftakesmay becreatedj notwithftanding all the Au- 
thors care and accuratenefs poffible,from the carelefaefs 
or neglect of the Graver : This I noted in the two 
Tables of the learned and accurate Mathematician,, 
P. JEgidips Fruncifcus de^ Gotigpks, (whofe skill and 
care from other works of his and other Obfervations of 
this Comet I ana fufficiently aflured of) and found 
that by the firft table upon the f \ of Dwwber, 1664.it 

wa 



[21] 

was in 4! of i. in Longitude, and in 33 f of Southern 
Latitude 5 but by the fecond it is placed at the fame 
time in 4 nr for its Longitude, and in 34J of South La- 
titude. And this error is not only committed in the 
place of the Comet, but alfo in the place of the fix'd 
Stars : for Riget in the firft Table is placed in 30I South 
Latitude, andini2f3i for Longitude, but in the fe- 
cond in 3 if South Latitude, and in n i nr for Longi- 
tude : both which differ confiderably ftom the place 
of itaffigned by Riccioli and Grimaldi^ according to 
whofe Obfervations it fhould be in 3T. n ; South La- 
titude, and T2Mi'. 40". 31 in Longitude. 

Now if there be thefe differences to be remarked in 
the Obfervations of one, we cannot but expedV that 
much more difagreement fhould be found between 
thofe which have been made by differing perfbns in difi 
fering places, and with differing ways, and differing 
Inftruments. And upon examination I have found it no 
better : for from comparing fuch Obfervations as I 
ftavereceived from feveral parts of the world, even of 
thofe which have feemed more than ordinarily exad, I 
find them for the raoft part fo unaccurate, that though 
they fufficiently manifeft that the Comet of 1664. 
which lafted above four months, was vifible in molt' 
parts of the world, and feen to pafs in all thofe places, 
pretty near in the fame way amongft the fixed Stars. 
Yet they are fo far from manifefting the Parallax , that:- 
fome of them make the place of the Comet to be quite 
contrary to what Parallax would make it 5 fome of the 
Southern Obferva tors placing k much' more South-, 
wardly than thofe of the North. Others indeed o£ 
them make the Parallax fo great, that one might ghefs 
it to be not fo far removed from the Earth. Something 
indeed in the general might be gheft of the way of that 
Comet amongft the fix d Stars, efpecially when it ap- 
proaches them pretty near.-but for exaftnefs of Calcula- 
tion for Parallax, they were no way ufeful, And even , 

U 3 in:. 



in the former ufe too it fecms very doubtful for com- 
paring the Charts of the Comets way amongft the fix'd 
Stars publilhed by that diligent and unwearied Qbfer- 
ver Mr. Hevelius of Dantziek^, the above-mentioned 
P. Gottignies, ProfefTor at Rome , and Monfieur Petit 
of Park, I find, that the two former make the way of 
the Comet to lie below the Star in the Bill of Corvus 3 
whereas the later, though in a Latitude interpoied be- 
tween the parallels of the former , makes it to lie a- 
bove, or to the North of it : and with him agree fome 
Obfervations which I have feen of Monfieur Hugenius. 
Other differences I found between thofe Tables in the 
way of the Comet of 64. near the middle of its arch 3 
wherein Monfieur Hevelim all the way places it more 
Southward than either Monfieur Petit , or P. Gottig- 
tties : for whereas both P. Gettignies , and Mounfieur 
Petit make it pais above the Star of the third magni- 
tude in the right fhoulder of Lepus, Monfieur Heve- 
lim makes it move below it,which feem to be afcribable 
to Parallax. But I fear much cannot be concluded of 
certainty from them. 

I fhall not trouble the Reader with a multitude of 
other Hiftories, which I have received concerning that 
Comet of 64. nor with the difagreements of them one 
with another , and perhaps of moft with the truth. 
They have given me fiifficient trouble in the examinati- 
on of them, having little other benefit from them, fa ve 
only this , that I was thereby informed what a man 
might think of a great number of Aftronomical Obfer- 
vations that have been made : for,faving the exacf Ob- 
servations of fome few fuch, as Mr. Hevelius, Mr.Auront, 
P. Gettignies , &c. truly diligent and accurate men, 
the greater the Collections of Obfervations are , the 
more trouble and difficulty is created to the Examiner^ 
they not only confounding one another , but perplex- 
ing thofe alfo which are real and perfect. 

Now the reafons or caufes of thefe inconveniences 
feem to be thefe. 

Firft, 



Firfly the want of accurate and knowing Qbferva- 
tors. 

Secondly, Thefcarcity of convenient Inftruments. 

Thirdly, The Imperfe&ion of the Tables of the fix'd 
Stars. 

For the Obfervators, 'tis not enough to know how 
to manage an inftrument, or to have a good eye , or a 
dextrous and fteady hand 5 but with thefe there muft 
be joyned a skilfulnefs in thetheorkal and fpeculative 
part, and add to all a love and delight in the thing it 
lelfj and even all thefe will fignifie but little, without 
convenient and accurate Inftruments ; fuch as may be 
eafily manageable and fufficiently exact. 

Thefirft of thefe the love of the ftudy being in it 
felfthemoft excellent, or the encouragement of Prin- 
ces , Noblemen, and other Patrons of this Learning 
muft procure : and where both of thefe concur, thence 
moftisto be expe&ed , and moft fruit hath hitherto 
been proceeded 3 though there are not wanting divers 
eminent inftances where the firft reafon hath been the 
only inducement. 

Astothefecond, I have already in fomeof my for- 
mer Lectures deferibed feveral convenient ones for. 
thefe purpofes 5 and therefore I (hall not here add any 
more concerning it. 

But as to the third, I hope the indefatigable labour, 
and skill of Monfieur Hevelim will fhortly fupply the 
prefent defect, though it had been much to be wiuYd, 
that the Inftruments he had made ufe of had been fitted 
with Telefcopical fights. Thefe Tables , if well done, 
will alone (as to the bufinefs of Comets at leaft) fupply ■, 
the place of all other Inftruments almoft, fave only a 
thread, efpecially if they be fo delineated in Tables af- 
ter the Tangent projection, as that the minutes of eve- 
ry degree may be very diftinguiihable, which will not- 
fwell the Maps of the Heavens into an extraordinary 
large volume, and maypoffibly bethecheapeft Inftru- 
ment for. this purpofe an Aftronomer can be furnilhed 

withal ; 



I H 1 
withal 3 for having fuch a volume of Tables, it will be 
very eafie with a thread and one's eye , fcreen'd only 
with a fpe&acle made of a thin plate of Brafs , with a 
final! hole through it, inftead of a glafs, to obferve what 
place the Comet poflefleth amonglt the fixt Stars : for 
having by the help of the faid thread obferved what 
two Stars lie in the fame line with the Comet on one 
fide of it, and what other two Stars lie in a line with 
it, which is at right angles ("as near as may be) with the 
former line, by finding out thofe four Stars in the Ta- 
bles , ordered according to the Tangent proje&ion, 
and with a Ruler, drawing lines over them refpeclive- 
iy, where thofe lines do interfedr, there will be the true 
place of the Comet, from which it will not be difficult 
to find out the true Longitude and Latitude of it by a 
Se&or with Tangents. Now as thefe Tables of all the 
•fixt Stars vifible to the naked eye, would ferve for find- 
ing its place whilft very big and fwift of motion^ fbthe 
like Tables of the fmall Telefcopical Stars that lie near 
its way, when almoft difappearing , and moving very 
flow, will by the help of a pair of meafuring Compaf- 
fes placed within the eye- giafs of the Telefcope, and a 
fteaight line or hair drawn crofs it, ferve to find the true 
motion and way of it, when only vifible i with a Tele- 
fcope : according to which method 1 made the annexed 
Schemes, and Obfervations of the laft appearances of 
the Comet. 

Now fince neither from my own,nor from any other 
Obfervations that I have hitherto met with , there can 
be any certain conclufion drawn of the diftance of thefe 
Comets, fave only this , that their diftance was very 
great, and much higher than the body of the Moon 
becaufe elfe there muft have been a confiderable Pa- 
rallax caufed by the Diurnal motion. The next enqui- 
ry will be, what other ways there are of knowing its 
diftance. Now though none could be more demonftra- 
tive than the Parallax found this way by the Diurnal 
motion, yet there are fome other which feem more eafie 

arifijBg 



arifing from the confederation of the motions that may 
be thought to be concern d in the producing the appea- 
rances. And though they be wholly hypothetical, and 
fo need fome other arguments to prove the ground and 
principles on which they are founded, yet fince there 
are not very many conliderable ones wanting to 
make them probable and rational, I fhall here add 
fomewhat of my inquiries after the diftance, pofition, 
motion, magnitude, &c. of thefe Comets by thefe 
means. 

Of thefe ways there are feveral depending upon (e- 
veral fuppofitions which produce very differing effe&s, 
as to the magnitude, diftance, motion, and way of the 
fame Comet. 

The fuppofitions are thefe : 

Either that the Earth moves in an annual orb about 
the Sun, as the Sun is fuppofed by others to move 
about the Earth : Or that the Earth is perfectly fix d, 
and hath no fuch motion. 

Next, that the Comet moves either in a ftraightline s 
or in a curve line , and the curve is either a cirde, or 
fome other regular or irregular curve. 

Further that the motion of the Comets in thefe lines 
is either by equal or unequal fpaces in egual times. 

Now according as we take this, or thofe of thefe dif- 
fering fuppofitions, and compound them together , Co 
will the produd of them be ftrangely differing. Amongft 
the great variety of compofitions of thefe principles or 
fuppofitions, thefe feem the moft fimple, and confe- 
quently being any otherwife proved , will beft deter- 
mine the true diftance and way of the Comet. 

Firft, To fuppofethe Earth to ftand ftilL, and the 
Comet to move equal fpaces in equal times in a circle. 

Secondly, To'fuppofe the Earth to move in an an- 
nual Orb about the Sun , and the Comet to move 
through the iEther or Expanfawt^ equal fpaces in equal 
times in a ftraight line. 

Thirdly, To fuppofe the Earth to move fas above) 

E in 



% 



in its annual Orb, and the Comet alfo to move equal 
fpaces in equal lines in a circle. 

The other are indeterminate and infinite, and no- 
thing can be concluded from them as to the diftance., 
magnitude, motion , &c. of Comets 5 for the line or 
Way of the Comet may be placed at any diftance, if we 
will fuppofeit moved in an uncertain curve , with une- 
qual degrees of velocity: And indeed, uponafuppo- 
fal of an inequality of motion, nothing of its way or 
diftance can by any of thefe fuppofitions be found out. 
This fault had that of Tyche Brahe, where he fuppofed 
an unequal motion of it in its Orb about the Orb of 
Venw^ which was founded upon the firft Hypothecs, 
but had introduced into it fame inequality of motion 5 
befides his own fuppofition, that it was moved about 
the Sun, and the Sun about the Earth, See the fifth 
Figure. Kepkrs way , which was after the fecond 
Hypothecs, had the fame fault 5 for he fuppofed the 
annual motion of the Earth , and the motion of the 
Comet in a flraight line , but introduces an accelera- 
tion of motion in the Tangent towards the latter 
end. 

The third way I have here taken, and from the bed: ' 
obfervation I could meet with, I have delineated its re- 
fpe&s or angles to the Sun : and accordingly fuppofing 
it to move equal fpaces in equal times, in a curve which 
for fb much of it as the Comet was obferved to pais 
was very near a Circle,! found this Circle would fall as 
it is exprefs'd in the feventh Figure, where 'tis obvious 
to take notice , that when the Comet was neareft to 
the Earth, namely, about the 19. or 20. of December ■, 
that it was not nearer than an eleventh part of the di- 
ftance of the Sun$ that on the 23, it was twice as far, 
that on the 29. it was four times as far 5 that on the 1 5.. 
of January it was as far as the Sun , and on the 14. of 
February it was above twice as far diftant as the Sun. 
That this way or Orb of the Comet is here bended fo 
as (if it were an entire Circle;) one part of it would 

go 






f>7] 
go without the Orb of Jupiter , as the other which is 
here delineated comes within the Orb of the Earth 5 
that the plain of this Orb is inclined to the plain of the 
Ecliptick about 18 degrees, that if from feveral parts 
this Orb perpendiculars be let fall upon the Plain of the 
Ecliptick, thofe perpendiculars (hall fall in an Ellipfis, 
part whereof fliall fall within the Orb of the Earth in 
51, and the oppofite without the Orb of ^ in*». That 
the Comet moves a Sextant of this Orb in about 130 
days, and confequently if its motion (hould continue 
the fame in fuch a Circle , it would appear about Fe- 
bruary, March, or April, 1667. but being fo far remo- 
ved towards the South Pole, will here hardly be feen : 
but by thofe that live towards the South, it may appear 
to have fomefuch motion by the South Pole, as that 
of 1 61 8. had by the North. And 'tis notimpoffible, 
but that the Comet of 1618. might be the fame with 
this, if we fuppofe the Nodes of it to have a motion 
contrary to the order of Signs : and that the fame Node 
which in this Comet, according to this fuppofition was 
in m, was then about W or £ : butthefeas conje&ures 
Ifhallnotinfifton, be c au(e neither in this , nor in that 
have we Obfervations fufficiently accurate to build 
any Theory upon. Now though upon thefe fuppofiti- 
ons the motion and appearances of the Comet feem to 
be very regularly, and very naturally made out, yet 
'tis not the only Hypothells for that defign : nor do I 
believe it fo evident a demonftration for that end , as 
Ibme would fuppofe 5 though for other reafons I am 
apt enough to think that opinion of the Earthsmotion 
very probable : but the motion of this Comet is fo well 
made out, by the contrary fuppofition, that I think it 
may be alledged for a greater argument againft the mo- 
tion of the Earth , than for it: for if we only grant 
one of the former poftulata , namely, that the body of 
the Comet is moved equal fpaces in equal times , and a 
quite contrary pofiulatum to the former - namely, that 
the Earth remains fix'd as to an annual motion, we may 

E 2 find 



C 38] 

find alt the obfervations of this Comet , efpecially the 
mod: accurate of them, to happen fo , that the Comet 
being fuppofed to be moved 4n a great Circle, whofe 
convex fide is turned towards the Earth, whofe center 
is extended towards the fix'd * in ® $ and whofe Semi- 
diameter is about fixfcore times the neareft diftanceof 
the Comet from the Earth, and the Comet be fuppofed 
to be moved very near equal fpaces in equal times, 
we (hall find , I fay , all the appearances moft exa&ly 
folved, and indeed much more exa&ly than by the 
other fuppofition I was able to find any 3 for by this 
fuppofition both the magnitude, longitude, latitude,re- 
trogradation, ftation, and direction of the Comet is 
moll: exactly made out as any one might have found 
that fhould have by this means examined with me the 
obfervations I have hitherto either made or met with : 
and indeed all the Obfervations hitherto have fo well 
anfwered this Hypothefis, that I do almoft promifemy 
felf to be able to fee this Comet a month or fix weeks 
hence, after the Sun has pall: by it 5 if by its exceeding 
elongation it be not quite grown out of fight , as it is 
now indeed already fo exceeding dim, and faint, that it 
cannot be feen without a very good glafs , which will 
endure an exceeding big aperture : nor could I thefe 
two laft nights perceive it, though the Air were clear 5 
but the reafon I attribute to its nearnefs to a fixed 
pfrof r : This Hypothefis is explained in the feventh 
Figure- By this fuppofition the return of the Comet 
will be much longer, and the time of feeing of it much 
more uncertain 5 becaufe the curvature is fo little that 
the making the circle a twentieth , or a fixteenth part 
bigger or lefs , does not much alter the regularity, 
whence 'tis exceeding difficult, unlefs we had much 
more accurate Obfervations than I have hitherto met 
with , to determine exactly the bignefs of the circle, 
and consequently the time of the return. 'And .by this 
fuppofition the Comet may be fuppofed either nearer 
or farther from the Earth at any diftance, which is not 

con- 



[2 9 ] 
contradi&ed by a Diurnal Parallax 3 that is, it may be 
fuppofed either above Saturn, or below the. Moon, or 
in any place between 5 by fuppofing only , that 
the farther the neareft part of the Circle is diftant from 
the Earth , the greater muft that Circle be , and the 
fwifter the motion of the Comet in it : to prove which 
affirmation,let in the Eighth figure A be the Earth, BCD 
the Orb of the Comet fuppofed very near the Earth, 
and E F G the Orb of it fuppofed at a greater diftance : 
let H be the center of BCD, and I of E F G, and let 
A C, be to C H, as A F, to F I, all the lines drawn from 
the point A, fo as to cut the Circles BCD and E F G, 
(hall divide thofe Circles EF G, and. BCD, into fimi- 
lar fegments: as let ABE be a line drawn cutting 
thofe Circles in B and E: I fay, the Arch BC-ftiali be 
fimilar to E F. In which Hypothefis if we have toge- 
ther with the place of the Comet when ftationary, the 
place of it when in its greateft celerity, perige, or the 
places of it when of the fame celerity on each fide of 
its perige, we have from thence the proportion of the 
Radius of its Orb to the perigean diftance, and confe- 
quently all the other diftances, the line in which it ap- 
pears when ftationary, being the Tangent to the Circle 
in which it moves, as ABE, to which a Perpendicular 
raifed at B B E, and produced till it cut the line A C, 
(produced) at H H I, it gives the Center of its Orb 
H H I, and the proportions of the lines A B, AC, B H 
= H C, or of A E, A F, E I = F I, the Angle B A C, 
being given by obfervation. So that by this Hypo- 
thefis the Phenomena of the motion and bignefs of 
the Comet will be folved, though fuppofed of any 
diftance. Nor are thele the only Hypothefes by which 
the hitherto obferv'd Phenomena may be folvd; for if 
we will admit an unequal motion, fuch as is now gran- 
ted to all the Planets : and if further . we will admit it 
tQ be moved in anElleipfis, or other fuch like curve, 
there may be divers other Hypothefes that will folve the 
Phenomena 5 fothat the Comet may be fuppofed to 

E 3 have 



have no motion at all as to Longitude, but only as to 
Latitude : that is, it may be fuppofed to be moved in 
anElleipfis, defcribed in a plain which (hall beat right 
Angles with the plain of the Ecliptick , and the ways 
of the Earth in it : it may be fuppofed alfo to have been 
mov'd direct, according to the order of the figns, that 
is, to have been firft about Gemini ^ in refpeft of the Sun, 
and to be now in fome part oiLeo: And it is not irapof- 
fible to folve the phenomena of its periodick or proper 
motion, though it be fuppofed not lb high as the Moon, 
and that the motion of the Earth paffingby it did real- 
ly alter its motions, had there not been made fome Ob- 
fervations about the Parallax of it , which prove it 
higher : fo that according to this or that Hypothefis 
which we take, the time of its return, if permanent, 
will be longer or fboner. 

And thefe Hypothefes may be fo various, that till re- 
gulated by very exa&Obfervation of the Parallax, 'tis 
not to be hoped that the appearance of a Comet can be 
certainly predicted : So that I fear the prophetick fay- 
ing of Seme a , Erit qui demon 'Jiret aliquando in qui bus 
Comet£partihu4 errentjur tamfedu&i a ceteris ecintMuanti 
quakfque (mt'j will hardly be verified at this time by the 
help ofthisprefent Comet.Though in truth I cannot find 
by the examination of feveral of them, but that they all 
feem to promife very fairly a return of it : for all the 
Calculations I have hitherto made of its motion, feem 
to caft it into a circular, and not a into ftraight line, as 
Kepler fuppofed} and indeed upon examining even 
Keplers own Calculations of thofe Comets which he 
obferved, and has endeavoured to make to move in a 
ftraight line, I cannot find that any of them will be 
found to move equally in fuch a line: but to fblve the 
appearances, he is fain to make them move in fuch fup- 
pofed ftraight lines,by a line of Tangents,that is, to make 
the motion of Comets accelerated the further they are 
moved 3 all which Phenomena may be very eafily 
folved by fuppoiing them to have moved equal fpaces 

in 



C3i D 

in a curve or circle. The phyfical reafbn indeed feems 
pretty difficult , by what means it Should be confin d 
or bound fo as to move in a Circle : but this is no more 
than is ufually fuppofed in all the Planets , and with- 
out fuppofing a kind of gravitation throughout the 
whole Vortice or Cesium of the Sun , by which the 
Planets are attra&ed , or have a teudency towards the 
Sun , as terreftrial bodies have towards the center of 
the Earth. I cannot imagtn how their various moti- 
ons can with any fatisfa&ion be imagined , but that be- 
ing granted (for which had I now time, I could alledg 
many reafons, and may doit hereafter on another occar 
fion) not only the reafbn of all the irregular motion of 
the Planets may be eafily found , but the reafon 
alfoof the ftrange and various motions of the Comets. 
The reafbn why its Beard is for the moft part oppofite 
to the Sun , which was another Query , of which I 
have already faid fomewhat of my fuppofitions , and 
thall now add, that the brighter fpot or kernel in the 
middle did feem'to be fome kind of body, which 
though it be not a&ually burnt , may yet by the en- 
compaffing fluid ^Ether be diffoived and wafted, and 
thofe diffoived parts may afcend upwards, or from the 
center of the Sun, (which feems indeed to be the cen- 
ter of gravitation throughout the whole fyfteme of it.) 
To illuftrate which explication, I could produce feve- 
ral experiments which would make a perfeft reprefen- 
tation of the phenomena of the body , and beard of 
the Comet : I fhall only inftance in one. Take a very- 
clear long Cylindrical Glafs , which may hold about a 
quart of water 3 fill it three quarters full with water, 
and put into it a quarter of a pound of Oyl of Vitriol, 
and in the midft of this fufpend by a fmall filver wire, 
a fmall wax-ball , rould in filings of iron or fteel , and 
you may plainly obferve a perfed reprefentation of the 
Head,Halo,and Beard of the Comet 5 for the menftruum 
falling on,or diflbl ving the iroa,there is a continual erup- 
tion of fmall bubbles 5 aud diflolv'd particles from all the 

fides 



fides of this body 3 and after the eruption they all af- 
cend upwards from the center of the earth 5 for being 
of a much lighter confidence than the anbient liquor, 
they are by the greater gravity of that , continually 
protruded upwards. The fame appearance may be 
made with any kind o^menjimum^ and a convenient 
diffoluble body lufpended in it 5 fo that if we fuppofe 
the iEther to be fomewhat analogous to a menfiruum, 
and that there is a gravitation towards the center of 
the Sun, if the Nucleus or head of the Comet be fup- 
pofedfuch a diflbluble fubftance, the phenomena of 
the fhapeof the Comet may, I think, be rationally ex- 
plained. Now that the ./Ether may have fuch a kind 
of propriety, feems tome to be argued from this, that 
the Air about the Earth feems to owe its original to it, 
it being only a diffolution of terreftrial bodies into the 
j£ther, the Sther being the principal fluid body, and 
greateft part of this difldlution, and the fubftance of the 
Air,fome very few andfmall faline and earthy particles : 
of which elfewhere. By this Hypothefis the phenomena 
of the Comet may be folved 3 for hence 'tis eafie to 
deduce the reafon why the Beard grows broader and 
broader, and feinterand fainter towards the top: why 
there is a Halo about thebody^ for this will appear 
clearly in the experiment : why the Beard becomes a 
little defle&ed from the body of the Sun 3 for if the 
difToIving Ball be by the wire mov'd either this way or 
that way, thearifing fiream or bubbles- will bend the 
contrary: and to countenance this fuppofition, both 
in thofe Comets obferved by Tycho, Kepler, and alfo in 
this laft the beard was contrary to the motion 3 10 that 
the head or body going fafter , feemed to leave the 
beard or tail fomewhat behind : by this fuppofition alfo 
'twill be eafie to explicate why the beard is fometime 
bended, and not ftraight , and why it is fometimes 
brighter upon one fide than upon another } why the 
bottom of it is more round , and the other fides more 
undefin'ds and divers of the like phenomena. Againft 

this 



[33] 

this fuppofition it feems difficult to conceive whence 
fo vaft a body (Mould be generated 5 next , hdyv it 
fhould beabletofupply fuch a conftant ftream of a- 
(tending parts, and yet laft fo long as this has donei al- 
moft a quarter of a year. Thirdly , Whence fuch a 
newly generated body fhould receive fo great a degree 
of motion. In anfwer to which, I fay, 'tis not impota- 
ble but that the body of it may be as old as the worlds, 
and that it^ay have then received its firft determina- 
tion, or laws of motion , and may have ever fince pre- 
fer ved them, that it may have been all this time alio in 
diflolution,and yet not be quite wafted^and that it may 
continue yet for many ages before it be quite diffolved 
into the iEther. And to make this probable , divers 
experiments and realbns might be alledged , as that pf 
the flownefs of the wafting of many bodies , by the 
diiTolutionmadeonthembythe fire: the flownefs alio 
of the diffolution of multitudes of bodies in menjiruums. 
Arid I have already (hewn howfmall a quantity of dif- 
folved particles will be able to make as great a (hew of 
light: befides that, the motion of the afcending ftream 
or beard being but flow* there needs no very quick 
fupplyof other parts. We fee alfo into what a vaft 
quantity of fmoke a (mall parcel of a combuftible body 
may be turn'd. From all which particulars, 'tis not un- 
likely but that the Comet may be a body moved with 
a regular circular or elliptical motion as the Planets 
are, that it may be a body of fuch a constitution , as 
that the fluid iEther through which it paiTes, may dip* 
fblve it much after the manner as a mevfiruum ; (Tuch as 
Aqttofortiffipmt of Niter,e^J does a diiloluble body 5 
that by this means there may be a flow , but continual 
eruption of fomewhat opacous parts , which may by 
their diflblution afford a (ufficient quantity of light to 
make as great an appearance as any of the Comets, that 
this ftream or beard may by the refiftance of the iEther 
be a little deflected backwards in the fame manner as an 
afcending ftream of fmoke will be by the refiftance of 

F the 



[34] 
the Air, if the burning body be mov'd this or that way 
through it, that the body of the Comet may be both as 
ancient and as lading as the world - and that this which 
has lately appeared may have appeared heretofore, and 
may likewife hereafter appear again 5 that 'tis probable 
the neareft diftance of it was much greater than that of 
the Moon, that the length of its Beard was longer than 
its diftance from the Earth , and confequently feveral 
times longer than the diftance between the Earth and 
the Moon 3 that its vifible way among the Stars was 
, very differing from a great circle , efpecially towards 
the latter end,when it became retrograde 3 that its way 
through the iEther could not be fuppofed equal in a 
ftraight line , though it might be fuppofed equal in a 
curve or circle, that the exad way of it could r not 
be certainly determined by thebeft Obfervations J have 
yet met with : and that therefore the beft help we have 
to gheis of its way and diftance, is by its manner of mo- 
ving, as to appearance among the fixed Stars, which I 
have already (hewn to be explicable by various Hy- 
pothefes : for both the Earth and Comet may be fup- 
pofed to be moved, either both one way, or contrary 
ways, or crois ways 9 the Earth may be fuppofed to 
ftand ftill, and the Comet only to be moved , and the 
like. 

Thefe Requisites therefore being hitherto wanting 
in the Obfervations I have met with of this Comet , all 
that can be faid of it will at beft be but conjectural and 
hypothetical 5 fince nothing can be reafonably built 
upon thofe Obfervations where the truth of them is du- 
bious 5 wanting therefore found materials to work upon 
in this Comet , I had recourfe to the Obfervations of 
the noble Dane Tychc iBrahe, being fufficiently fatisfied 
both of the ability, induftry, and veracity of that ex- 
cellent Author, who left nothing unattempted for the 
perfecting of fuch Obfervations as feem'd to him requi- 
lite for the compleating a Hiftory of that Comet which 
appeared in 1 577. And from thofe Obfervations of his 

A. 



[35 1 
I endeavoured to trace the way of it according to fe- 
veral hypothefes 5 and found, that fuppofing the Earth 
not to be moved with an annua! motion, but only a 
diurnal about its own Axis, the way of Comets will fall 
in a line very near approaching the nature of a circle, 
though neither into an exact circle, nor an exad eilipfe 5 
and therefore feems irregular, and not at all probable, 
Again, fuppofing it moved about the Sun, as Tycho has 
done, we find from his Calculation of it, he was fain 
to allow it a quicker and (lower motion in its Orbit, to 
folve the Phenomena, which feems to me but a (hift, 
that will ferve to help out any lame Hypothefis what- 
foever : And that granted , and the Parallax of the 
Comet unknown, I will undertake very eafily to make 
out almoft any Hypothefis, which is the fault alfo of 
Mr. Horox his hypothefis , wherein he fuppofes the 
Earth to be moved about the Sun , and the Comet like 
a Rocket to be (hot out of the Sun, and by degrees to 
return to it again 5 in which Hypothefis indeed there 
feems to be much more reafon for an inequality of mo- 
tion, though not in the manner as he has placed it 5 
'twas very rational that the motion of itatfirft, if call: 
out of the Sun, (hould be very fwift 5 but then it ought 
likewife to have accelerated its motion in the fame 
manner in its return back to it again, which it does not 
in his Hypothefis 5 for a done or any other heavy body 
being (hot up into the Air , does make its return back 
again to the Earth, almoft by the fame degrees of velo- 
city, by which it afcended from it : almoft , I fay, be- 
caule the refiftance of the Air does fo far impede the 
motion of the body through it , that it never fuffers it 
to acquire the fame degree of velocity with which it 
was firft (hot upward. This is fufficiently evident from 
a Pendulum^ which if it be thrown upwards, and be 
fuffered to return back, it will never rife again on the 
oppofite fide to an equal height, with that it defcended 
from, on that fide towards which it was throMn: but 
befides, in his Hypothefis he feems to take no notice at 

Fa all 



aH of the Latitude of the Comet, which feemed to 
carry it much farther off from the Sun, when he ftp* 
pofes it to be returning nearer. And indeed upon 
the whole his Hypothefis feems rather a product of 
chance than of any contrivance. For he in endea- 
vouring tofet off the Longitude of the Comet ac- 
cording to Tyeho's Tables , and to trace its way by 
fuppofing the Earths annual motion, making ufe al- 
ways of the fame Radius to (et off the aipecl, or ap- 
parent angle of it with the Sun, his line of Chords he 
made ufe of did always direft the point of his Compaf- 
festothe place where he folates the Comet „ as may 
be eafily found by examining the ninth figure 5 where 
you may find that he places the Comet always equally 
diftant from the Earth, and that diftance is always 
equal to the diftance of theStm, ^wriich^hasJi) many in- 
conveniencies and improbabilities , that I fhall not i«- 
fifbfartheronitj efpecially finceldonot find that he 
beftowed any farther pains in explicating or cultiva- 
ting this his Hypothefis, than only the bare deiineati* 
on of this ninth figure. But to return to Tycho's Hy- 
pothefis, if that be true, why did not the Comet 
again appear after a certain fpace of time ? and why 
could not he have foretold when it fhould again ap» 
pear, as well as he could predkt the appearance of 
Venues about whofe Orb he fuppofes it to circulate > 
Khallpafs by feveral other very material objections 
that might be made againft that his foppofitiorj, becaufe 
many of them mightbe made alio againft his Hypothe- 
fis of the Heavens in general, which I fhall the rather 
omit, becaufe I do not find he has many followers in 
that fuppofition 3 the generality of Aftronomers em- 
bxacingrathertheC^m/>^Syftern, efpeciaiiy a* it is 
refined and rectified by the ingenious Kepler* 

Laftly, I endeavoured to trace the way of the Co- 
met from Tycho's Tables > according- to Replers Hypo- 
thecs 3 which was, that the appearances of the mo- 
tion of,the Comet were afcribable tQ two caufes 3 

namely. 



namely, the motion of thfe Earth about the Sun in its 
annual Orbit, and the motion of the Gomet in a ftraight 
line, not accelerated according to the proportion of the 
increafe of Tangents 5 but upon fuppofition that it 
mov'd equal fpaces in equal times : (for I cannot -imagine 
what reaibn he had to iuppofe its motion to be accele- 
rated, and much lefs why he (hould aflert it to be ac- 
cording to the proportion of Tangents, which in a lit- 
tle time rauft neceflarily come to move infinitely fwift : 
than which nothing is more hard to be granted ) And 
I found it after many trials and efiays to fail in a 
ftraight line, inclining to the plain of theEclipttck by 
anangle of 47.40. and cutting it in 9 degrees of Scorpio} 
if computed out of the Sun, and moved falter by half 
than the Earth in its Orb 5 and this to fo great an ex- 
a&nefs to aniwer all the Obfervations of Tycho^ that 
from a very large Scheme which I drew of it on a plain, 
I could never find many minutes difference 5 Co that I 
concluded that to be the moil likely Hypothefis for 
that Gomet, it feeming to folve all the feveral Pheno- 
mena of the motion and magnitude of the Gomet, with 
the leaft imaginable difficulty , and to be moil agree- 
able with my phyfical notions of Gomets : For, firft it 
only fuppofes a folid body moved in a fluid , with an 
almoft dired motion. I fay, almoft direct;, becaufe for 
fome phyfical reafons, as 1 have faid before , I imagine 
it not exactly ftraight, but inflected a little towards the- 
curvity of a circle, which I (hall prefently endeavour 
to explain farther in this Comet. Next, it fuppofes that 
body to move in that line almoft equal fpaces in equal 
times 3 I fay, almoft equal D becaufe fome of thofe equal 1 
fpaces may be increased by an accelerating eaufe or 
principle, fuch as that of a gravitation towards the bo- 
dy of the Sun, placed in the center of its Vortice or 
Syftem , when the motion of the Comet carries it to- 
wards the Sun, and maybe diminifti'd from other impe- 
ding caufes, fuch as the impediment of the fluid me- 
dium through which it pafles, and the attraction of the, 

F3 Sua. 



[38 3 

Sun operating on it when its motion carries it farther 
and farther off from it : befides, 'tis not unlikely, but 
that the attraftion of the Earth, or fome of the other 
Planets may have fome kind of influence on it, efpeci- 
ally,when its line of Dire&ion does fomewhat nearer 
approach thofe attra&ive points, But the deflection 
from a ftraight line is always (b much the left by how 
much the fwifter the body is moved, and by how much 
the farther off its line of trajecfion is perpendicularly 
diftant from thofe attracting bodies. According to 
this fuppofition of mine, I have endeavoured to make 
out all the appearances of this laft Comet, taken no- 
tice of is the beft obfervations I have yet met with, 
amongft which I find no one of the Parallax fatisfa&o- 
ry, as in the tenth figure, let S reprefent the Sun, ORB, 
the Orb of the Earth, ACDEF, a bended or curve 
line in which the Comet is fuppofed to move : the 
Comet then coming into the Sphere of the attractive 
power of the Sun,* by the ftraight line P A G, at A, the 
power of the Sun worketh on it, and by degrees at- 
tracting it towards its own .Center by that time the 
Comet hath moved to C, the attractive power hath de- 
flected its direcl: courfe from P A G ? to C H, and fo the 
Comet would continue to move in that ftraight line 
GH, but it is ftill defle&ed fo, that at D, it moves to- 
wards I, but the gravitation of the Sun attracting it, 
defle&s it from that line towards E, and fo from E to F, 
when it begins again to Jet out of the attractive beams 
of the Sun, andfb it will continue to proceed, as if it 
had come to that point by the line M F L, the reafon 
of which is the great velocity of thefe bodies, which are 
generally much fwifter in their motions than the Earth 
or other Planets are fuppofed to be, in theirs. We 
muftfeek out fome other way therefore of finding of 
the diftance of Comets than the commonly ufed : I mall 
therefore fomewhat further explain the contrivance I 
newly invented for this purpofe, by which not 
only the Parallax of the Comet but of the Pla- 
nets 



C 39 3 

nets alfo may be found with great facility and ex- 
a&nefs. 

Having a large Telefcope prepared fas I formerly 
dire&ed ) with Eye-glafles capable of taking in an 
Angle of about two degrees at once, and furniftied 
with a dividing Scale, obferve when the motion of 
the Comet or Planets is not too fad, the pofition and 
diftances of the (mail -"fixed Stars which are next ad- 
joyning to the moved body whofe Parallax you would 
find 5 of thefefmall fixed Stars you (hall feldommifsa 
fufficient number, which will be taken into the glafs 
atonce if at lead: the objed-glafs be allowed a very 
large aperture 5 and having found fuch Stars as will be 
convenient for your purpofe, be very diligent in taking, 
by the help of the dividing Scale, the exaft diftance 
of them one from an other, and when the body is high- 
eft above the Horizon, vm>< in or near the Meridian, 
by the fame means take the exaft diftance of it from 
two or three of the neareft and moft confpicuous fixt 
Stars about it, and by the help of a plumb-line, hung 
likewife within the cell, near the dividing Ruler, find 
exaftly the pofitions of all thofe bodies you take no- 
tice of to the Perpendicular or Horizon,which may be 
eafily enough done, if together with a Plumb-line or 
Perpendicular plac d within the glafs you have alfo a 
fmall Diagonal thred faftned to a ring, whofe circum- 
ference is divided into 360 degrees,and moveable fo as 
by the finger eafily to be turned any way, by which 
means this Diagonal thred may be made to crofs over 
any two of the bodies you obferve, and by obferving 
what diyifion of this divided limb the Perpendicular 
cuts, it will be eafie to determine the exaft pofition 
of thofe Stars to the Horizon, this fame may be 
done by the dividing Scale alio, if that be fixt in a 
divided Circle which is movable, in the fame manner 
as the thred is fuppofed to be. This Obfervation, with 
all other circumftances of it is likewiieto be repeated 
at the fetting or riling of the Planet or Comet, and a- 

g a " m 



C 40 ] 
gain the next night when it comes to the Meridian, 
and in each of thole obfervations the exact time is to 
be noted by a time-keeper, and the altitude by fome of 
thole I have before defcribed, for by comparing thefe 
three obfervations together it will be very eafie to find 
what irregularity in its motion is afcribable to its Paral- 
lax. And this will be Co much the ealier becaufe the 
examination and reduction of it may be done (with as 
great exactnefsas the obfervation can be made,) by the 
help only of Ruler and Compafles, for all the distan- 
ces will be let oft by equal divilions of ftraight lines, 
the line alfo of the periodick motion, whether of the 
Comet or Planet, efpecially if the obfervations be made 
when the body is near an opposition with the Sun, 
which is much the beft time, will be with fufficient ex- 
a&nefs taken for a ftraight line, and the motion in 
that line may be fup poled by equal fpaces in equal 
times 3 for the difference between the Tangents of the 
centefms of a degree to two degrees is not increaied 
much more then -—^ that is not a quarter of a centefm 
of the hundredth part of a degree, which is much more 
exact than I fear our obfervations will ever be. 

Another way of finding the Parallax may be by the 
help of exact obfervations made by feveral perlbns at 
the fame time , in places much differing in Latitude, 
though as near as may be under the fame Meridian 
("becaufe of laving the trouble of Calculation, and for 
being allured that the obfervations were both made 
exactly at the fame time J each perfbnby the help of ve- 
ry long Telefcopes obferving the exact diftance of the 
body from thefmallfixt Stars next adjoyning. 

A third way of finding the Parallax of Comets is 
wholly new, and though hypothetical (as fuppofing 
the annual motion of the Earth, and the motion of 
the Comet in a right line through equal fpaces in equal 
times) yet 'tis founded upon a Problem in Geometry 
(invented by the incomparable Mathematician, Doctor 
C.Wnn) which is truly noble. and wholly new, and 

though 



though it had been of no ufe in Aftronomy, deferves 
none of the meaneft places in Geometry, by the help 
of which (which is much more than either of the 
other ways is capable «of) one may eafily find the 
true parallax of the Comet, from any four exaft 
obfervations of it, made at differing times in the fame 
place : Nor does it require fo nice and accurate Inftru- 
ments and Obfervators as are altogether neceffary in 
the other ways. The Problem as I received it, is this. 

(Problema. 

Datn quatuor linen utcunque duUn (quarum nee tres 
font parallels nequeab eodempunBo du&&) quintam ducere 
qu£ Z quatuor primo datn in tres partes fiecetur r attorn 
& pofitione datas. 

Sint inFigum 13, 14, 1 5, 1 6, !"/,<& 1 8, quatuor re&£ 
ADC, BEC,AE,BD, produ&sverftn K,y,<p,M,opor- 
tet quintam ducereui K M, qus fiecetur a primo datn in fig- 
ment a KN, NO, M,fiecun4um datas rationes R, S, Jl 
Fiat ut R ad S, T,fimul fiumptas it a C D,adC F. Rurfius 
utTadS,R, (imuljumptas, it a EC, ad CG, ducJnautem 
AGH,BFH,a mutua inter fieUione H, ducantur HyK, 
H(p M, parallels nimirum linen AC,BC, qu£ medi<e inter- 
jacent inter extremes, BD,AE. Denique inter punffia ex- 
tremarum K M, ducatur ReBafiecans mediae in NO. Dico 
figment a- KN, NO, M, ejfe in Data ratione RST. 

6)uoniamF D, paralkla efi ipfi HK, ergo ut C D, ad 
CF,itaK y, ad y H, & quomam yN, paralkla efi ipfi 
HM, ergo, utKyadyH, it a K N, ad N M, ergout 
KN, adNM,ita CD,adCFh fed CD,ad CF,efiut 
Rad S,T, fitnul fiumptas, ergo KN, efi ad NM,utR, 
ad S T, [imul fiumptas. Similiter quoniam E G, paralkla 
efi ipfi MH,& <p0, ipfi HK, demonfiiraiur MO, 
ejffe ad K, ut T ad S,R, (imul fiumptas. §)uare tres 
KN,NO,OM erunt ad invicem ut R, S, T, ergo duci- 
tur linea K M, cujus tria fiegmenta a quatuor lineis datis 
intercept a funt in data Ratione R,S,T, <& fervata qui- 

G • clem 



dew pojtiione Jive ratwnum or dine U,S,T, quod era* 
faciendum. 

From the invention of which Problem 'twill be 
very eafie by any four obfervations Graphically to 
defcribe, or Geometrically to calculate the true di- 
ftance of the line of the traje&ion of the Comet, 
and confequently toanfwer all thofe queftions that can 
be demanded concerning the bignefs of the body and 
head,and concerning the bignefs and length of the blaze, 
and concerning the diftance of it from the Earth in eve- 
ry part of its way when it was neareft the Earth, when 
neareft the Sun, where it cuts the Plain of the Ecliptick, 
feen from the Sun, and where ihcn from the Earth, 
with what Angle it was inclined to the faid Plain, how 
fwift the motion was, that -is, what length it pafled, in 
what time,when it mud: appear Stationary ,when Retro- 
grade, when difappear, and the like. 

According to this method I received at the fame 
time,("whilft it yet appeared very vifible to the Eye, and 
was not Retrograde J the. way of the firft Comet de- 
lineated by the faid perfon, which did very near folve 
all the appearances preceding and fubfequent, which 
I have therefore here annexed in the Table expreffed in 
the 19.20.and 21. figures,where in the 19. is delineated 
the Place of the Sun in the Center of the Circle v 5 N, 
D, J, ~ ,, which reprefents the annual Orb of the Earth 
about the Sun, the points between N and D reprefent 
the places of the Earth in that Orbit in the days- of 
November, and the lines drawn from them to the points 
in the ftraight line, reprefent the lines in which the 
Comet appeared in refpecl: to the Sun 5 in like manner 
the points between D and I, the places of the Earth 
in December, and the lines drawn from them to the 
ftraight line, as before the vifible places of the Comet 
at thofe times^ &c. The 20. figure reprefents fingly 
the feveral Longitudes of the Comet at feveral times 
feen from the Earth. And the 2 1. reprefents the fe- 
v-eral .Latitudes^ at the feveral times, together with the 

true 



[43 ] 
true diftances of the Comet at thofe times, both which 
are made out of the 19. figure, where E at the end of 
the line reprefents the Center of the Earth, from which 
to the figures in the prickt curve-line, are the true di- 
ftances of the Comet,the Perpendiculars from thofe fi- 
gures to the line E C are the figns of the Latitude of 
the Comet from the plane of the EcliptickE C, the 
aforefaid diftances being made the Radii. 

Now though according to my former Delineation 
the Comet feemed to take a circuit, as if it would 
within three years return to its former pofition, yet I 
am not wholly convinced that it moves in a circle or 
Ellipfe, but I rather incline to the incomparable Kep- 
krs opinion, that its natural motion tends towards a 
ftraight line, though in fome other fuppofitions I dif- 
fer from him. 

At firft that the Comet perfeveres exa&ly in a 
ftraight line. Secondly, that after it has paft its Pe- 
rige it accelerates its motion in proportion to Tangents 
of equal Angles. Thirdly, that it either is extinguifht 
diffipated, broken in pieces, or burnt out into afhes. 
Fourthly, that it receives all its light from the Sun. 
Fifthly, that if the blaze were not made by the beams 
of the Sun palling through the head of the Comet, 
and fo carrying the parts along with them, the blaze 
would not be oppofite to the Sun. Sixthly, that the 
caufe of the bending of the blaze is the refradion of 
the Suns raies in the body, and their being bent by 
the iEther as with a wind (which is the opinion that the 
Ingenious Defcartes follows alfo.) To thefe I cannot 
confent, and I have many objections to feveral other 
of his opinions concerning this matter , which would 
be too tedious to infert 5 only I (hall add, that 
having traced feveral of the Comets according to the 
beft obfervations I could get, I found it very difficult 
to make their motion fall in a ftraight line, unlefs it be 
granted that their 'motions are really accelerated and 
retarded in that line, which feems not fo probable, at 

G 2 leaft 



C 44 1 
leaft not in thofe parts of their tranfit where be places 
them. And particularly by tracing the way of this 
Comet of 1664. it is very evident that either the ob- 
fervations are falfe, or its appearances cannot be folved 
by that fuppofition, without fuppofing the way of it 
a little incurvated by the attra&ive power of the Sun, 
through whole fyftem it was pairing, though it were 
not wholly ftayed and circumfle&ed into a Circle, as 
Ihave already mentioned. 

That it is not extinguifht or quite burnt out, when it 
eeafes to appear, I argue from this, that I was able to fee 
it with a Telefcope above a month after it difappeared 
to the naked Eye, as may be feen by the obfervations I 
have annext in JFVg.4. and had not the cloudy weather 
and the light of the Moon, and nearnefsof the Crepufcu- 
lum hindred, I fuppofe I might have feen it much longer, 
as I am apt to believe the great one in 16 18. might have 
been feen feveral months longer, if it had been diligent- 
ly followed with Telefcopes, it difappearing in fuch a 
part of the Heavens as might have been feen every clear 
night between the Crepufculummd Dawning. 

Nor can I fuppofe it to receive all its light from 
the Sun, fince if fo it would follow, that the Nucleus 
in the head, would have a dark (hadow oppofite to 
the Sun, the contrary of which has always been ob- 
ferved. Nor can I well underftand that the Sun 
beams- are like a dream of water, carrying the parts of 
the Comet along with them fo as to make its blaze, 
fince no fuch efTecl; is found of them here with us upon 
the Earth:Nor how they fhould come to be bended like 
fmoke, fince we obferve no fuch property of light in a 
uniform medium, fuch as in probability the ^Ether is. 

Thefe were my thoughts about thofe Comets 
which appeared in 1664. and 166$, which I have 
found in feveral loofe papers of Lectures, read in 
thebeginning of 1665. And I have not had the op- 
portunity of making many obfervations fince, con- 
cerning . Comets, lave thefe two lad, .in. which I had 

no&. 



not the convenience of obferving any thing certain 
concerning its motion or Parallax. And therefore I 
applyed my felf to mark as near as I could the true fi- 
gure of it, through a fix foot Telefcope, and to take 
notice of as many circumftances as thefhort time I had 
would permit, which though they were very (hort and 
tranfitory obfervations, and I wanted time to repeat 
them fo often as I could have defired, yet even from 
them I was fufficiently fatisfied, that I had reafon to 
adhere to my former conjecture, that the light of the 
Comet did not depend wholly from the reflection of 
the Sun beams, from the parts thereof, but rather from 
its own light, for upon well confidering of the form of 
this Comet, I manifeftly faw that the middle of the 
blaze was brighter than the fide parts thereof, and 
efpecially that part which was immediatly oppofiteto 
the Sun, was the brighteft of all, which would have 
been otherwife if the light had depended wholly from 
the defle&ion of the rays of the Sun, for one might 
rationally conclude that the Nucleus or Star in the mid- 
dle, which reflected fo great a quantity of light fhould 
have caufed a darknefs in the parts behind it, as we fee 
all ftrong reflecting bodies do, and confequently that 
the middle part of the ftream or blaze, efpecially that 
which was next the body fhould not have been fo 
bright as thofe other parts to which the light of the 
Sun had a more free accefs, unlefs it maybe faid that 
evenjthe Star it felf, though it feem fb bright, is. not- 
withstanding not fb Denfe, but that it admits rays e^ 
nough to pafs through it unrefledted, to inlighten the 
parts behind it. But this feems not fo likely, , fince be 
the body of the Star fuppofed a thoufand times thinner 
than a Cloud (which yet tis hard to fuppofe, fince it 
gives fo confiderable a reflection J yet it being, in all 
probability ten thoufand times bigger in bulk, the rays 
in paffing through fo great a bulk, muft needs meet 
with more obftru&ion than in the thinneft Cloud, 
and yet we find that there is no Cloud fo thin, butcafts 

G 3 fhadow, 



C4<n 

fhadow oppofite to the Sun, and therefore in probabi- 
lity this would do the like, but I diligently obferved 
that there was no fuch appearance here, but the con- 
trary, that is, that where the fhadow fhould have been, 
there was the lighteft part of all the blaze, and con- 
fequently in probability it did depend upon fome other 
caufe than a reflection of light. 

It is a hard matter to affign the particular caufe of 
its light, but it feems from thefe circumftanees to be 
very probable that it was (in part at leaft J from its own 
nature, whether that might be fomewhat of that of 
the Sun and Stars, or of that of our fire, or of that 
of decaying fifh, rotten wood, glow-worms, &c, or 
of that of the Ignis Fatuus, at Land or Sea, or 
like that of Sea-water, or a Diamond, or like that of 
the falling meteors, or Star-fhoots, it will be very hard 
to determine, unlefs one had a much greater flock of 
obfervations to build upon. But it may poflibly be 
fomewhat of the nature of them all, though it agree 
not in all particulars with any one of them. All thefe 
ways that I have named teeming to agree in one parti- 
cular, and that is an internal motion of the parts which 
fliine, whether that motion be caufed by fome exter- 
nal menftruum diflolving it as in fire, andlgnes fatui, 
or an external motion, ftroke, or impulfe as in a Dia- 
mond, Sea-water, and poffibly fome Ignes fatui, or 
from the parts of the bodies working and diffolving one 
another,as in decaying fifh, rotten wood, glow-worms, 
or whether it be fufceptible of a much more fubtil 
impulfe, even from light it felf, as the Bononian (tone, 
and Blitdwines Phfbphorus,which feems to be fo harmo- 
nious (as I mayjfo (peak) to the motion of light, that 
a new motion is thereby raifed in it, and continues 
for fome time to move of it felf after the impulfe or 
influence ceafes, not much unlike the unifon firing, 
or other founding body, which in Mufick receives a tre- 
mulation and found from the motion and found of 
the unifon bodv, or firing that is (truck. 

To 



E 47 ] 

To me It feems moft probable that the body and 
parts of the Comet are in a ftate of diffoIution,whether 
that diffolution be caufed by the parts of the iEther 
through which it paffes, after the manner as a Torch 
is diflolved by the air, or whether by the internal 
working of the condiment parts one upon the other, 
as in Gun-powder 5 fliining Fiftt and rotten Wood, I can- 
not determine 3 but I rather guefs it to be in fomc 
things analogous to the one,and fomewhat to the other, 
though not exaftly the fame with either. And this I 
conceive from the figure and make of the thining parts, 
for if it had been of the fame nature with a Torch', 
the blaze would have refembled that of the flame of 
a Torch or Candle, that is, the fides would have been 
brighter, and the middle darker, as I have fhewn in 
my Lampas? whereas it was very manifeft that the mid- 
dle of the blaze was brighteft, and of that blaze that 
which was next the Star ox Nucleus was brighter than 
that which was further off ; whereas inflame the con- 
trary is very obfervable, as I have in the fajd Trea- 
tife fhewn. 

From the (hape of the figure, the manner of its diffo- 
lution feems to be thus. The Star or Nucleus in the mid- 
dle, feems to be the fiwes or fource from whence all the 
light proceeds ; this we fuppofeto be a denfe body en- 
eompaft with a very fluid body (fuch as the ^ther feems 
to be) but of fuch a loofe and fpongy nature, as that 
the iEther doth caufe thofe parts which are contiguous 
to it, to be diffolved and expanded into it felf. This 
diffolution and expanfionl conceive doth generate or 
eaufe the light that feems to proceed from it, that 
diffolution caufingfuch a motion of the iEther, as is 
neceffary to produce the appearance of light 3 now fo 
long as any part thereof remains in diffolution, fo 
long doth it continue to fhine, as is alio obfervable in 
the flame of any body burning in the air, but when 
the part feparated from the body is quite diffolved in- 
to the iEther, the effeftof Alining ceafes, as it doth 

alfo 



C 48 ] 

alfo in the parts of flame. Now I have obferved that 
the blaze is fo very much rarified, that firft the iEther 
I conceive comes very freely to every particle of the 
body after it is feparated from it, but efpecially to 
the outermoft, and continues to be incompaffed with it 
fo long as till it be quite diffolved into it, which I con- 
ceive to be at a little farther diftance from the head than 
the greateft length of the blaze feems to be to our fight. 
And further I conceive that the outward parts being 
thus incompaffed more perfectly with the free and un- 
difturbed iEther, are fooner diffolved into it than thofe 
©f the middle, and confequently the fides feem firft to 
difappear, and the middle parts continue their fhining 
to a much greater diftance from the Star in the head s 
though fomewhat alfo of that appearance may be 
afcribed to the difperfing and rarity of the parts near 
the fides. 

The Nucleus or Ball in the middle of the head, 
-which I have called the Star, I conceive to be diffol- 
ved equally on all fides, and the parts which are diffol- 
ved or feparated from it, I conceive to fly every way 
from the center of it, with pretty near equal celerity 
•or power, like fo many blazing Granadoes or Fire-balls, 
thefe continue their motion fo far toward the way 
they are (hot, till the Levitation from the body of the 
Sun defied them upwards, or in oppofitionto the Sun 
intoaParabolick curve,in which Parabolick curve,e ve- 
ry fingle particle continues its motion till it be wholly 
burnt out, or diffolved into the iEther. Thefe are con- 
tinually fucceeded by new feparations from the afore- 
iaid body in the fame manner as tis obfervable in a 
burning, (teaming, or fmoaking body in our air, or a 
diffolving body incompaffed with its proper menftru- 
um, as I before mentioned, and will fo continue until 
the whole be at length diffolved into the iEther, 
through which it paffes. 

It hath been demonftrated by Torricellius, of bul- 
. lets or other bodies caft or (hot upwards, that the fame 

or 



[49] 
or equal bullets difcharged or ftiot out from the fame 
point, with the fame degree of ftrength, but with 
differing degrees of inclination to the Horizon, each of 
them (hall be moved in a parabolical line, and every 
one of thofe parabolical lines (hall touch a paraboli- 
cal line, whofe axis is the perpendicular, and whofe 
apex is diftant from the faid point, the full altitude of 
the perpendicular (hot : So that fuppofing in the twenty 
fecond figure, A to be the point from whence all the 
fhots are made with equal velocity, A C the greateft 
height of the perpendicular (hot, and A D the greateft 
Horizontal random at 45 degrees of inclination, and 
fuppofe EDCDE a parabola paffing through thofe 
points D C D, all the (hots made with equal bullets, 
with equal velocity from A, but with all variety of in- 
clination between the perpendicular upwards, and the 
perpendicular downwards that touch the faid paraboli- 
cal line, and confequently if there be an indefinite 
number of fuch balls continually flowing out of the 
point A, with equal degrees of celerity every way 
difperfing themfelves equally in orbem, the whole ag- 
gregate of fuch an emanation will make a folid para- 
bolical conoeid EDCDE. Now about the point 
A, if we fuppofe a Sphere asBBBB, and from 
this Sphere an indefinite number of fuch equal Balls 
be thrown off perpendicularly to the fuperficies 
of it, from every point thereof, with equal ce- 
lerity at their leaving it, thofe emanations will form 
alfo a conoeid, which will be very near the fame with 
the former: And if this Ball in the middle be fuppofed 
a burning and mining body, and that all thefe emana- 
tions have every one of them equal light in proportion 
to the Globe BBBBA, the effect produced hereby 
will perfedly referable the appearance and figure of 
Comets, if at leaft the Parabolical conoeid be inver- 
ted 3 which will fomewhat explain the manner how I 
conceive the figure of the Cometical body is naturally, 
and moft proportionably formed 5 for if the efTed-of 

H iuch 



[. 5® ] 
fucfr an emanation of Chining bodies be examined, it 
will very plainly exhibit the exad and true apparent 
figure of Comets, as they may be feen through a good 
Telefcope, which is to me a very great argument, that 
'tis the genuine caufe of its ihape and figure : Now 
though the Comets appearance be this way caufed, 
and io a man might conceive the Globous body 
would in a little time (by fo copious an emanation) be 
confumed, yet I do not believe that it doth in a fhort 
time wafland. difperfe the whole Ball, nor can I con- 
ceive that the difappearing of thofe blazing bodies to- 
ward the latter end, does depend upon their diffoluti- 
on (though poffibly that may fomewhatdiminifh them) 
but that rather is to be afcribed to their diftance and 
pofition in reipecl: of us : Though this I remember I 
obferved very manifeflly in that of i664-that the body 
toward the latter end of its appearing was very much 
lefs in proportion to the radiations about it, than it 
feemed to be at the beginning, but whether that might 
not be partly afcribed to the great diftance it then was 
from us, and the turning of the head pretty near to- 
wards us,and thence the fpreading of the Tail (appear- 
ing beyond it,) might add to the breadth of the radia- 
tion about ttizNudests, I will not pofitively determine. 
Now though for explication fake, I have compared 
the parts feparated from the body of the Comet to 
blazing Granadoes or Fire-balls, yet I would not be 
underftood to fuppofe thefe parts fo feparated to be 
of any very large bulk, for I fee no neceffity to fup- 
pofe them bigger than the Atoms of fmoke, or the 
particles of any other (learning body, or than the parts 
of the Air, which make the body of it appear thick, 
and hazy 5 nor do I believe that all the light of the 
Star, head, amd blaze, does depend only upon the 
fhining of the diffolvmg body and particles thereof: 
but I do fuppofe that it doth proceed both from the 
reflection of the Sun-beams from thofe parts, and alfo 
from an innate and momentaneous light produced by 

the 



the aftion of diffolution wrought on the parts by the 
incompaffing iEther. 

It may poffibly feem very difficult to fuppofe that" 
the diffolution of the parts of the Nucleus , by the in- 
compaffing iEther, (hould caufe or imprefs fo violent 
a motion into the feparated parts, as to make them 
depart from it to the (pace of four or five Diameters, 
before it be overpowered by the power of Levitation 
from the body of the Sun, and fo derlefted into a pa- 
rabolical line upwards. It may likewife feem ft range 
to fuppofe that the iEther fhould have fuch power in 
it, as firft to diffolve a body into it felf, and fecondly 
to caufe a {tuning, and thirdly to caufe a Levitation of 
the diffolved parts upwards 5 whereas I (uppofed be- 
fore ("and I think 'tis very manifeftj) that they caufe a 
gravitation downwards, towards the Center of the 
Sun : But to thefe for explication, I anfwer that we 
need not go far for inftances to make thefe things 
probable, the Atmofphere about the Earth, as I have 
formerly mentioned in my Micrographia, I take to be 
nothing elfe but the diffolution of the parts of the 
Earth into the incompaffing iEther 5 for the proof of 
which, I could bring many arguments, were it here 
a proper place, by which I could moft evidently de- 
monftrate the thing to he as I. have afferted. It is here 
evident that this iEther doth take up the particles of 
bodies to a very great diftance from the furface from 
which they were feparated, and it doth not only raife 
them but fufteins them at thofe heights,nor is this pecu- 
liar only to the ./Ether when a menftruum, but to all 
diffolving menftruums in general. 

As to give one inftance, in ftead of many, we find 
that Gold (the heavieit of all Terreftrial bodies we yet 
know,) being diffolved by Aqua Regis, is taken up in- 
to it, and kept fafpended therein, though the pam 
of the Gold be fifteen times heavier than the parts of 
the Aqua Regis. So Pit-coal though very heavy, is 
yet taken up" into the Air, and kept fufpended there- 

H 2 in. 



i% though it will be found to be fome thoufands of 
times more ponderous than the menftruum of the Air 
that keeps it fufpended. 

Many reafons I could produce to (hew the great 
power of the iEther, and the univerfality of its afti- 
vity almoft in all fenfible motions, but referving them 
for another Difcourfe hereafter, I ffiall at prefent, on- 
ly, mention thofe fuppofitions which feem to have 
the greateft difficulty, in this Theory, vim, how the- 
dillolution of the parts of the Star by theincompaffing 
$)ther ihouldcaufe light, and fecondly how it ihould 
caufe an aftual Levitation of the diiToking particles up- 
wards. For the explication of thefe two difficulties, 
I muft at prefent crave favour to explain them by ex- 
amples taken from operations of Nature in the At- 
mofphere wherein we live, very fimilar and analogous 
to them. Firft, for the production of light, we find 
that the Air incompaffing the fleams of bodies pre- 
pare^ by heat or otherwife, and made fit for diffolu- 
tion, doth fo operate upon them, as to make them fly 
and part afunder with a very impetuous motion, info- 
much that the fmall particles or Atoms of the difTolved 
bodies, do not only leave one another, but depart and 
dart out with fo great an impetuofity, as to drive off 
all the incompaffing Air from their Center from 
whence they flew, and this I take to be the caufe not 
only of their Light, but alfo of their Levity upwards, 
this may be feen very plainly by the fmall parts of 
crackling Char-coal, which upon the blowing them 
with Bellows, and fo crowding a great quantity of the 
frefli menftruum' on them, fly and dart afunder with 
great celerity and noife, but is abundantly more evi- 
dent in the kindling of Gun-powder, where the im- 
petuofity is fa very great as to drive away not only all 
the incompaffing Air but all other bodies, though ne- 
ver fofolid, that hinder its expansion, in the perform- 
■ .ing of which operation the ./Ether hath a great (hare, 
as I may hereafter jhew, 'tis very probable that the 

JEthcv. 



C » ] 

iEther in the fame manner diffolving the particles of 
the Star, eaufeth the Atoms thereof to fly afunder 
with fo great an impetuofity as to leave a vacuity 
even of the parts of the .zEther, which flying afun- 
der doth not only caufe light by impreffing on the 
iEther a ftroke or pulfe which propagates every 
way in Orbem, but maketh fuch art agitation of the 
the iEther, as caufes a rarefaction in the parts thereof, 
whilft the parts that are once actually feparated, by 
continual rebounding one againft another before 
they come to be at reft and quietly to touch each- 
other, prolong that ficft reparation or vacuity be- 
tween them. 

This Explication, though it be fomewhat difficult, 
yet I hope it is intelligible, and may be, with 'proba- 
bility enough, fuppofed to be the true caufe of the 
appearance, whilft there is nothing therein fuppofed 
which isnotmanifeftly the method of Nature in other 
operations 5 and though the fuppofition even of the 
iEther, may feem to be a Chimera and groundlefs 5 
yet had I now time, I could by many very fenfible 
and undeniable experiments, prove the exiftence and 
reality thereof, and that it doth a&ually produce not 
only as fenfible effects as thefe I have named, but very 
much the fame, and many others much more cofidera- 
ble, which by Philofophers have hitherto been afcri- 
bed to quite different caufes. 

Had I been able to have made fome other obfervati- 
ons f which! defigned, if I had had the opportunity of 
feeing it, fome of the fucceeding Nights J I fhould have 
hoped to have explained feveral other difficulties con- 
cerning the nature of the body and blaze of Comets, 
but being therein prevented, I muft leave them till I 
can make fome further obfervations on fome Comets- 
that may hereafter appear. 

In the mean time that what I have difcourfed con* 
eerning the light of Comets, may not feem fo altoge- 
ther paradoxical and unintelligible as fome mayimar- 



H 3 gin% 



t 54 J 

gine, I have here added an account of fome trials and 
obfervations made on ihining fubftances of natures ex- 
ceedingly differing from thofe that are commonly to 
be met withal. And this I the rather do, not only 
becaufeit affords an inftance of Chining where there is 
no Air, but that hereby I may enlarge the limits of 
their imagination, who (hall confider of this fubject* 
For nothing is more apt to mifguide our reafoning 
than a narrow and limited knowledg of caufes, we 
are not to conclude the body of a Comet a fulphureous 
vapour exhaled from the Earth and kindled above, 
becaufe here are fuch vapours obferved and fuch ef- 
fects produced, nor a collection of Sun beams made by 
a Lentiformed vapour, after the manner of aBurning- 
glafs (as fbme eminent Writers have lately done,) be- 
caufc fome fuch appearances may be Artificially pro- 
duced in a fmoaky or thickned Air 3 iince if we dili- 
gently inquire, we may find that light which is the 
moft fenfible quality of Comets that affects our fenfes, 
may be, and really is produced by very many, and 
thofe very differing ways. In Nitre and Sulphur 
kindling each other by heat, we have one way 5 in a 
body burning in the Air a fecond, in a heated Iron or 
Glafs a third, in a piece of Iron hammered till red hot 
a fourth, in rotten Wood and decayed Fifh a fifth, in 
Glow-worms, Scohpondras^ and other living Worms, 
and in the fweat and excrements of other living crea- 
tures a fixth, in a Diamond rubbed a feventh, in Dews 
Ignes fatui, &c. an eighth, in Sea-water a ninth, in the 
Bonotiian ftone,and in the Phofphorus Baldwini (which 
I take to be much of the fame nature) a tenth, in the 
Phofphorus of Mr. Kraft an eleventh , and poffibly 
wholly differing from all thefe, may be the iigjk 
of the Sun, a twelfth, and that of the Star may dif- 
fer from that of Sun, and the Comet may be differing 
from all the reft. Whether they be fo or not, the be- 
ing acquainted with the feveral proprieties of them 
will the better enable one to judg of what is perti- 
nent 



£55] 
ncnt to be obferved in Comets, in order to find out 
which is concerned. 

The Phenomena of moil: of thefe Chining bodies 
are very common and obvious, and therefore need- 
lefs to be added 3 but that of the Bononian ftorie pre- 
pared, and that of the Phofphorus Baldwim (lately 
difcovered by Wh.Baldwine) are rare and hard to be 
got,and the effefts of them are wholly differing from all 
the ways I have yet met with, and will therefore prove 
Experiment a Cruris, highly inftrudive in the Theory of 
Light, of which more hereafter. As for the Phejpho- 
ros Fulgnrans of Mr. Kraft (more fcarce and rare than 
the other) 'tis wholly differing from any of the reft, 
and very ft range and furprifing, at leaft it appeared fo 
tome, who had the good fortune to be prefent at a 
good part of the experiments made by the Author in 
the prefence and at the Chamber of the Honourable 
Robert Boyle, Efq; that great Judg and Promoter of all 
curious inquiries into Nature and Art, who at my ear- 
neft intreaty, was not only pleafed to commit to wri- 
ting what he obferved, but (for the information of 
Curious and Inquilitive Naturalifts,) to give me liber- 
ty here to publifti it. 



l57l 



<i/[ Jkort Memorial of fome Obfenations 
made upon an Artificial Subjlance> thai 
fhines without any precedent lUuftra* 
tion. 




September ^ i6jy* 

N Saturday the fifteenth of this month 
I was after fupper vifited by Mr. Krafts 
a famous German Chymift, who was 
pleafed to come and (hew me a ftrange 
rarity he hath newly brought into Eng- 
land, to the fight whereof he allowed me to invite fe- 
veral members of the Royal Society, he being defirous, 
beeaufe the matter he imploys is very coftly and of 
difficult preparation, to be a good Husband of it, and 
by (hewing it to feveral curious perfons at once, to 
exempt himfelf from the need of ihowing it often. 
The Company being met, the Artift took out of a 
pretty large box he had brought with him, divers 
Glafs VelTels and laid them in order on the Table. The 
largeft of them was a Sphere of Glafs, which I gueffed 
to be four or five Inches in Diameter, being hollow 
and intire, fave that in one place there was a little 
hole, at that time ftopt with fealing wax, whereat to 
pour in the Liquor, which feemed to me to be about 
two Spoonfuls or fomewhat more, and to look like 
muddy-water made a little reddifh with brick-duft or 
fome other powder of that colour, he alfo took out of 
his Box three or four little pipes of Glafs fealed, oro- 

I therwife 



e m 

therwife ftopt at both ends, being each of them fome* 
what bigger than a Swans quill;, and about five or fix 
Inches long, and having at one end a fmall frag- 
ment or two of that matter that was to (hine in 
the dark. 

He likewife laid upon the Table three or four Vi- 
als of feveral fizes, but none of them judged capable 
to hold above very few Ounces of water : in each of 
which Vials there was lome Liquor or other, that was 
neither tranfparent nor well coloured, which Liquors I 
confefs upon his making no particular mention of what 
they were to do,I was not curious to compare together,, 
either as to quantity or as to colour. Befides all thefe 
fubftances which were fluid, he had in a fmall Cryftal- 
line button Bottle, a little lump of matter, of which he 
feemed to make much more account than of all the Li- 
quors^ and which he took out for a few moments to 
let us look upon it, whereby I faw that it was a con- 
fident body, that appeared of a whitifh colour, and 
feemed not to exceed a couple of ordinary Peafe, or 
the kernel of a Hafel Nut in bignefs, fbme other things 
s tis poffible Mr. Kraft took out of his Box, but neither 
I or (for ought I knowjothers of the Company took 
notice of them, partly becaufe of his haft, and partly 
becaufe the confufed curiofity of many fpec~tators in a 
narrow compals, kept me from being able to obferve 
things as particularly and deliberately as I would glad- 
ly have done, and as the occafion deferved. Which 
Advertifement may I fear be but too applicable to a 
great part of the following Narrative. 

The forementioned Claries being laid in order upon 
the Table, the windows were clofed with wooden- 
fhuts^ and the Candles were removed into another 
Roomby that we were in 3. being left in the dark we 
were entertained, with the enfuing Phenomena. 



Though 



C 59 1 

I. Though I noted above that the hollow Sphere of 
Glafs had in it but about two Spoonfuls for three at 
moft) of matter, yet the whole Sphere was illumina- 
ted by it, fo that it feemed to be not unlike a Cannon 
bullet taken red hot out of the fire, except that the 
light of our Sphere lookt fomewhat more pale and 
faint. But when I took the liberty to hold this 
Clafs in my hand and (hake it a little, the contained Li- 
quor appeared to fhine more vividly, and fometimes 
as it were to flafh. 

II. I took one of the little pipes of Glafs for- 
merly mentioned , into my hand , and obferved 
that though the fhining matter had been lodged 
but at one end, yet the whole Glafs was enlightened, 
fo that it appeared a luminous Cylinder, whole 
light yet I did not judg to be always uniform, nor 
did it laflr like that which was included in the Vi- 
als. 

III. In thelargeft of the Vials next the Spherical 
already mentioned, the Liquor that lay in the bot- 
tom being fhaken, I obferved a kind of fmoke toaf- 
fcend andalmoft to fill the cavity of the Vial, and 
near the fame time there manifeftly appeared as it 
were a flafli of lightning that was confiderably di& 
fufed, and pleafingly furprized me. 

IV. After this I took up that fmall Cryftaline Vial 
that I lately called(by a name familiar in our Glafs-fhops) 
a Button-Bottle, wherein was contained thedryfub- 
ftance which the Artift chiefly valued, as that which 
had continued luminous about thefe two years, and 
having held that Vial long in my hand, in the fame po- 
rtion in reference to my eye, and lookt attentively at 
it, I had the opportunity to obferve ( what I think 
none of the Company did J that not only this ftuff 
did in proportion to its bulk, fhine more vividly than 
the fluid fubftances, but thaat which was the Pheno- 
menon I chiefly attended) though I could perceive no 
fmoke or fumes afcend from the luminous matter, yet I 

I 2 could 



C 60 ] 

eould plainly perceive by a new and brisker light that 
appeared from time to time in a certain place near the 
top of the Glafs, that there muft be fome kind of 
flafhy motion in the matter that lay at the bottom,. 
which was the caufe of thefe little conizations, if I 
mayfo call them. 

V. The Artift having taken a very little of his con- 
fiftent matter, and broken it into parts fb minute, that 
I judged the fragments to be between twenty and thir- 
ty, he fcattered them without any order about the 
Carpet, where it was very delightful to fee how vi- 
vidly they fhined 3 and that which made the fpeftacle 
more taking,efpecially,to me, was this, that not only in 
the darknefs that invironed them, they feemed like fixt 
Stars of the fixth or leaft magnitude, but twinkledalfo 
like them, difcovering fuch afcintillation as that where- 
by we diftinguifti the fixt Stars from raoft of the Pla- 
nets. And thefe twinkling fparks without doing any 
harm (that we took notice of ) to the Turky Carpet 
they lay on, continued to fhine for a good while, 
fome of them remaining yet vivid enough till the 
Candles being brought in again made them difap- 
pear. 

VI. Mr. Kraft alfo calling for a (beet of Paper and 
taking fome of his fluff upon the tip of his finger, 
writ in large Characters two or three words, whereof 
one being DOMINI^ was made up of Capital Letters, 
which being large enough to reach from one fide of 
the page to the other, and being (at lead: as Igueffed) 
invigorated by the free contact of the external Air, 
fhone fo briskly and lookt fo oddly, that the fight 
was extreamly pleafing, having in it a mixture of 
ftrangenefs, beauty and frightfulnefs, wherein yet the 
laft of thofe qualities was far from being predomi- 
nant. And this Phenomenon did in more fenfes than 
one afford us the mod of light, fince not only the 
Characters (hone very vividly upon the white Paper,, 
but approaching Jt to my Eyes and Noftrils, I could, 

difcerm 



difcern that there afcended from them a fume, and 
could fin ell that fume to be flrong enough, and (as it 
feemed to me ) to participate of the odour of Sulphur 
and of that of Onions. And before I paft from the 
mention of thefe refplendent Characters, I muft not 
forget that either by their light, or that of the Globe, 
or both by the one and the other a man might 
difcern thofe of his fingers that were neareft the 
ihining ftuff, and that this being held to the face 
though without touching it a fome of the confpi- 
cuoufeft parts, efpecially the Nofe, were difcovera- 
ble. 

VII. After we had feen with pleafure , and not 
without fbme wonder, the fore- going particulars* the 
Artift defired me to give him my hand, which when 
lhaddone D herub'd partly upon the back of it, and 
partly on my cuff, fome of his luminous matter, which 
as if it had been affifted by the warmth of my hand 
(hone very vividly, and though I took not notice of 
any thing upon my skin, that was either un&uousor 
rough, yet I often times tried in vain by rubbing it 
with my other hand to take it off, or manifeftly dimi- 
nifii its fplendor, and when I divers times blow'd up-' 
on fome of the fmaller parts of it, though they feemed 
at the inftant that my breath bqat upon it, to be 
blown out, yet the tenacious parts were not really 
extinguilht, but prefently after recovered their for- 
mer fplendor. And all this while this light that was- 
fo permanent, was yet fo mild and innocent that 
in that part of my hand where it was largely e- 
nough fpread,. I felt no fenfible heat produced by 

it. 

By that time thefe things were done 'twas grown 
late, which made Mr. Kraft, who. had a great way 
to go home, take leave of the Company after he had 
received our defer ved thanks for'the new, and inftru- 
dive Phenomena, wherewith he had fb delightfully 
entertained us. 



C 6* 3 

Becaufe Mr, Kraft had twice attempted to fire heat- 
ed Gun-powder with his Phofphorus, but without fuc- 
cefss probably bccaufe the powder was not very good 
(as by fome circumftances I conje&edj and becaufe it 
was not fufficientJy heated before the matter that 
fhould fet it on fire was put upon it, he promifed me he 
would come another time to repair that unfaccesfulnefsV 
And accordingly, On the two and twentieth of Sep- 
tember in the Afternoon I recived a vifit from Mr. Kraft, 
who told me he came to make good his promife of let- 
ting me fee that his {hiring matter was able to kindle 
heated Gun-powder, and becaufe no Grangers were 
prefent, I had the fairer opportunity to view it, which 
I was able to do better by day light, than I had done 
by its own light, for when he had taken it with a new 
Pen out of the liquor with which he kept it covered 
topreferve it, I perceived it to be fbmewhat lefsthan 
the nail of one of my fingers, and not much thicker 
than a (hilling, and I obferved that when it had lain a 
little while upon a piece of clean Paper and difcharged 
itfelf from its fiiperfluous moifture, it began to emit 
whitifti fumes which feemed to be very ponderous 

fince for the moft part they did not afcend but furround- 
ing the matter whence theyiffued, by their ftagnation 
made as it were a little Pond or fmall Atmofphere about 
it 3 fo that left it fhould waft too faft, he was obliged as 
foon as he had cut off a little corner lefs than half a 
pins head, to put the fluff nimbly back into the Vial 
out of which he he had taken it $ where I obferved it 
for a very fhort time to fend up exhalations into the 
liquor that covered it, and quickly after, as it were, 
quencht it. This done the Artift divided the little 
corner he had cut off into two parts, one of which 
he fpread as far as it would reach upon a piece of white 
Paper, which he prefently after held at a diftance over 
a chafing-difh of burning Coals, by whofe heat be- 
ing excited it prefently flaftit and burnt away, and I 
having perceived that there was another part of the 

Paper 



Paper which though not heeded by him, had been 
lightly beimeared by the fame matter, I held it over 
the Coals, but at a confiderable difiance from them, 
and yet this little matter nimbly took fire and burnt a 
hole- in the Paper. And to fatisfie my felf that the 
heat did but excite the luminous matter, and that 
twas this its felf that lighted the Paper, I held the 
reft of the fame piece of Paper far nearer the fire and 
kept it there a pretty while without finding it at all 
fcorchedor difcoloured. Laftly, the other part of the 
divided fragment of the hitherto mentioned matter, 
Mr. Kraft put upon the tip of a qui!, and having at a 
■ diftance from the fire, very well dryed and warmed 
fome Gun- powder upon another piece of Paper, he 
laid that Paper upon the ground, and then holding 
his quill upon it, as if it had been a match, within half 
a minute ("by my guefs) that powder took fire and 
blew up. 

Twill not perhaps be impertinent to add that on oc- 
cafion of the operation I obferved the Air to have 
on the fhining fubftance when freely expofed to it. 
I took a rife to tell Mr. Kraft that I prefumed it might 
be worth while to try whether his Phofphorus did 
Ihineby virtue of a kind of real or Cif I mayfo call 
it) living flame, which like almoft all other flames re- 
quired the prefenceand concourfe of the Air to main- 
tain it, or whether it were of fuch a kind of nature 
as the Phofphorus of the learned Baldwinus^ which I 
fufpe&ed tofhine not like a flame or a truly kindled 
fubftance 3 but like a red hot Iron, or an ignited piece 
of Glafs, wherein the Ihining parts are not repaired 
by fewel, as in other burning bodies, but are put by 
the a&ionof the fire into fo vehement an agitation as 
whilft it lafts fuffices to make the body appear lumi- 
nous. This conjecture Mr. Kraft feemed much to ap- 
prove of when I told him that the way I propofed to » 
emmme his no&ihca by, was to put a little of it into 
our Pneumatick Engine, and Pump out the Air, whofe 

abfence- 



I H 1 

abfence, if it were of the nature of other flames, would 
probably extinguiih, or very much impair its light, 
but yet fin@e he offered not to have the trial made * 
probably becaufehe had but very little of hisfhining 
fubftance left, I thought it not civil to prefs him. 
But to countenance what I faid of the nature of Bald- 
winus Phofphorm^ I (hall recite an Experiment that I 
purpofely made,to examin whether the prefence of the 
Air were neceiTary to the (Timing of this Phofphorus, 
as I had long fince found it to that of (bme pieces of 
fhining wood. 

Weexpofed for a competent time to the beams of a 
vigorous light, a portion of matter of about the, breadth 
of the palm of ones hand, which we had prepared to 
be made luminous by them. And then caufing the Can- 
dles to be removed (for we chofe to make tryal by 
night) we nimbly conveyed the matter into a receiver 
that was kept in readinefs for it, prefuming (as the 
event (hewed we might J that by ufing diligence the 
light would Jaft as long as the experiment would need 
to do ^ making haft therefore to Pump out the Air 
we needfully watched whether the withdrawing of 
it would, contrary to my con jedure, notably diminifh 
the light of the Chining matter. And after we had 
thus withdrawn the Air gradually, we tryed whe- 
ther by letting it return haftily, it would produce a 
more fenlible change in the matter (which had been 
purpofely put in without any thing to cover it, that it 
might be the more expofed to the Airs Action.) But 
neither upon the gradual recefs of the Air, nor yet 
upon its ruftiing in when it was permitted to return 
could we certainly obferve any manifeft alteration in 
the luminoufnefs of the Phofphorus, other than that 
flow decrement that might well be imputed to the 
time during which the experiment was making. It be- 
ing well known that this luminous fubftance requires 
no long time to make it decay, and by degrees to lofe 
all its light j fo that though once there feemedto one 

or 



t**1 

or two of the by-ftanders, upon the return of the 
Air, to be fome recovery of part of the loft fplendor, 
yet after repeated experiments it was concluded that 
the prefence of the Air was not at all necejjary to the 
fhining of our matter^ and it was judged moft proba- 
ble that the abfence or prefence of the Air, had no 
MAuifeft operation on it. I might add to this that per- 
haps the prefence of the Air is rather hurtful than ad- 
vantagious to this fort of lights, fince for having had 
a large Phofphorus that was much efteemed, and, whilft 
I kept it, exactly protected from the Air did very wells 
a part of the Glais that covered it, having by mif 
chance been fomewhat crackt, though none of the 
fplinters appeared difplaced, yet it feems fome of the 
€orpufcles of the Air made a drift to infinuate them- 
felves at thefe chinks (as narrow as they werej and in 
not many days made the matter ceafe to be capable of 
being made luminous as before. I cannot ftay to in- 
quire whether this unfitnefs or indifpofition may be 
imputed to the bare moifture of the Air, or to fome 
other fubftance or. quality that alone or in conjunction 
with the moifture, may fpoil that peculiar texture, or 
conftitutionthat fits the matter of the Phofphorus a£ 
lifted by the impreffions of external light to become 
luminous. This, I fay, I cannot ftay to examine^ 
though, That this Phofphorus is of a nice and tender 
conftitution, and eafily alterable, I was induced t© 
think, by rinding that the want of circumftances,, 
feemingly flight enough, would keep it from being 
made 5 and Iguefsthat a convention of circumftances 
did more contribute to the production than any pecu- 
liar and incommunicable nature of the matter.: Becaufe 
having had the curiofity to make fome trial upon 1© 
obvious a material as quick Lime, though the fucceis 
did not anfwer my deligns, yet, neither was it fo bad, 
but that fome luminous quality was produced in the 
Lime by the a&ion of the fire, and a faline Liquor 5 
and I fcarce queftion but other materials will be found 

K capable 



capable of being made luminous by the fame or the 
like operation, that is imploy'd by Baldwinm^ when 
that learned man (hall think fit to communicate his way 
to the Publick. But to return to what I was faying, 
that the contact of the Air might be rather hurtful 
than advantagious to the Phofphorus, I fhajl only add 
here as matter of facl;, (for my eonje&ures about 
Light belong to my yet unpublifht Notes, of the Ori- 
gine of Qualities ) that whereas the contact of the 
Air, though it were not free, did in a few days de- 
ftroy the luminoufnefs of a good Phofphorus, yet 
having included another in a Receiver, whence we af- 
terwards pumpt out the Air, this matter though in- 
ferior to the other in vividnefs was fo little fpoiled 
by lying open in our Vacuum, that at the end of 
not only fome weeks, but fome months, I found 
that the beams of a Candle paffing to it through 
the Receiver, would notwithftanding the Vacuum 
it yet continues in, fuffiee to re-excite in it a manir 
feft light; 



Thus far was the communication of this excellent 
perfon, who it's hoped may be further prevailed with 
to communicate thofe other accurate obfervations, 
and curious refearches he hath made concerning the 
light of the Bononian Stone, and the Phofphoros Bald- 
WJW4 which are indeed truly admirable , and very 
much differing from the ufual procefles of Nature 
for the exhibiting of light. 

Before I take leave of my Agronomical Readers, 
I fhall here acquaint them with fome Collections I 
have made of other Agronomical matters and difco- 
veries, which I hope will not be lefs pleafing to them 
than they were at firft tome. The Difcoveries are 
new 3 and not lefsfignificant.. The firft is, 



A let- 



167 1 

z4 'Letter from Johannes Carolus Gal- 
let, L.LfD. andTroyofi of the Church 
of St. Syrnphorean at Avignon, dU 
reBed thus. 

CLarijfimo Eruditijfimoque viro D.Johanm Dam'mi* 
co Caffino Matkejeos Profejjbri Celeberrimo, Afire- 
nomofr£fiantijJimo& Academic Regis fcienti amm alum- 
no meritijjimo. 

Conteining an account of his obfervation of Mercury 
paffing under the Sun. 
Mr. Gallet then acquaints Mr.Cajpm with his obferva- 
tion of $ fnh o and the whole method and procefsof 
his obfervation. Firft,he fitted two excellent Tekfcopes^ 
the Glaffes of which were given him by Mr. Jac. Bor- 
rellius 9 one of the Academy Royal of Park. The one of 
twenty three foot, he fitted with a Glafs covered with 
fmooke, placed in the outward focus of the Eye-Glafs : 
The other of three foot he fixt to the Arm of his Qua- 
drant of the fame Radius^ this was fo exquifite that 
compared with one of Diving which was chofen by 
the care of Honor ato Fabric and procured by Monfieur 
de Beauchamfs^ it was found to reprefent the obje&s 
clearer : By this the figure of the Sun was caft on an 
oppofite Table, on which he had drawn a Circle of the 
bignefs proper to the Diftance and Magnifying of the 
Glaffes to contain the whole Face of the Sun, and by 
Parallel Circles had fubdivided the fame into digits 
and Sexagefimals, he had alfo placed three threds in 
the interior focus of the Glaffes, that the mid dlemoft 
went through the Center, and the two outward 
touched the Limb of the Sun by their (hadow on the 
Table, he had alfo a Pendulum Clock that vibrated 
thrice in a fecond.Thus accoutred he watched the fifth 

R 2 and 



L6SJ 
and fixth day, from Sun rifing to Sun fetting, and the fe* 
venth after the Cloudy Sky had feemed to delude 
Eis curiofity till Eleven a Clock almoft, itthenbegan 
to open and difcovered to him Mercury got within the 
Eaftern Limb of the Sun, about ,J of its Semidiame- 
ter 3 at length the Clouds being difperfed, the Sun be- 
ing 27 45- high, or at io h. 54' V it felf marked out 
its own place in the disk of the by its own 
fhadow call on the Table by the fhorter tube. Then 
he difpofed the fhadow of the aforefaid thred fo Pa- 
ralel to the Equator, that this figure of the Sun fhould 
move between the outward ones, and that the middle 
ihould mark out the Paraleldefcribed by the Center of 
the Sun in motion,at the fame time he took the declina- 
tion of £ from this middle Parallel and the right Afcen- 
tion, by the number of Vibrations of the Pendulum,, 
from the Weftern Limb of the Sun, taken by the 
fhadow of a Perpendicular Crofs-line to the other 3. 
by the fame means, alfo he meafured the Diameter of 
the Sun and of Mercury. 

Then to the end he might give lefs caufe of doubt,ac* 
cording to his ufual cuftom, he procured feveral friends 
who were prefent and witnefles of all the obfervati- 
ons after the fourth mentioned in the Table. During the 
obfervation he took notice of thefe remarkable acci- 
dents. Firft, that Mercury through the long Tube was 
very black, and of an Elliptical figure whofe longed 
Diameter was Parallel to the Equator, but in the Spe- 
cies through the leffer Telecope, it appeared round 
and of a dusky red (like a fpot obferved by him in the 
Sun from the Ninth to the Fifteenth of J/?r//.)Secondly 9 
that the Diameter of Mercury going out of the Difc 
of. the Sun, when it toucht the periphery feemed to be 
of four times the Diameter it app: a ed of through the 
whole. Phafe, fo that Mr, Beauchamp, who watched 
. the exit with the longer Tube, whillt he himfelf min- 
ded the Quadrant in order to take the Altitude of the 
Sun 9 at the time of. the exit cried out, O how large do 



169 1 
fit fee the Diameter of Mercury now, it does not on- 
1 ly leave the Sun, but is confuted with it, or as it were 
melts into it, and prefently itvaniflit, the Sun being 
then 13. 23'. high. 

He further adds that before he leaves to (peak of the 
Sun, he will here infert an obfervation that he] had 
made of four fpots he had feen in the Sun in the firft of 
October laft (St. No.) with this his longer Telefcope, 
one on\y of which was vifible by the Species call: with 
theleflerClafi. 



O&ob. 
Die. hera 


Dectinat.macula prin- 
cipalis a paral. Cen- 
tri 4 


Differ entU temp, 
inter UmbumQ 
Occident. & 
maculam. 


Tempws tranft- 
tm difci So- 
laris. 


1 10 


4 44 aujir. 


I 4 20 


2 IO " ©■ 


2 10 


2 43 auft.- 


49 


2 IO 20 


3 10 30 


1 21 auft. 


99 40 


2 IO 20 


4 10 35 
6 10 


40 auft. 
3 boreal. 


2 5 40 
3 20 


2 IO 3P 
2 IO 4 



Thus fubmitting his method to the judgment of 
the Learned Cajfini, and earneftly defiring his thoughts- 
thereon, he ends his Letter, and Dates it from 
Avignon^ Nov. 21. 1677. 

To this Letter he fubjoins the obfervation it felfj. 
Intituled, 

Mercurius fub Sole vifus Avenione die 7. No- 
verab. 1677. Obfervattte me Joanne Carolo Caller, 
J.V.D. Pr<epopo Eccleji<e SanBi Symjhoriam Aveni- 
onenfis. 

The Contents of whicfr are, 

That defigning to obferve this paffage of # under Q 
he with his Tube watchfully looked for it in the Suns 
place, from the sthtothe 7th. day, withaTelefcopeof* 

m.^ ' 2-3" 



[ 70 ] 

23 fbot(a$abovej|heobferved a fpotofan elliptical 
figure which had already gotten a i 6th. part of the fe- 
midiameter of the Sun within the limb , and declined 
a little to the South in refpecT: of the parallel of the 
./Equator drawn through the Suns center , at io hours 
2 6 min. but the Clouds hindering he could not obferve 
its motion till it had alcended as high as the parallel : 
when the Suns altitude was 27. 45. or 10 a Clock 54 
minutes. From the quicknefs of its motion he foon 
found it to be 2 and not a fpot , and therefore 
he forfook not his Quadrant to which was fitted his 
three foot Telefcope and Table to receive the figure 
of the o but obfervedthe times of the Immerfions and 
theEmerfion of $ by the help thereof, being affifted 
by feveral of his friends who were witnefles of what 
pafled, and particularly by the Illuftrious Monfieur 
De Beauckamp, who with the twenty three foot Glate 
determined the Exit of Mercury whileft he himfelf 
took the Altitude of the Sun with his Quadrant, as i«r 
the tenth Obfervation. 



The 



C 71 J 

The Order of the Obfervations of Mercury 
feen under the Sun. 



The 
num- 
ber of 
the 
Phafes 
obfer- 
ved. 






Thenortb The difference of The 
Declinati- rhe time between the 
on of § f ranfit of Weft Limb 
from the of the Sun, and the 
Parallel of body of £ under 
the equat. the fame Meridian 
through collected from the 
the Gen- Pendulum Vibrating 
ter. 4 of a fecond. 



r 

2 

3 
4 
5 
6 

7 
8 

9 

10 



M.- S. 



o 

2 

2 

> 

6 

6 



3 

45 

40 

30 
30 

53 

55 

38 



diftanceiTheap-jThe hour 
of £ from parent [Collected by 
the Center ^altitude the 'Altitude, 
of the Sun. of die 
Sun. 



vib.Pend. M. S. T. 



545 
276 

258 

224 
164 
148 
13-2 
100 
80 
39 



55 
32 
26 

H 

o 54 

o 49 
o 44 

o 33 
o 26 

o *3 



c 
c 
c 

4c 
4c 
208 



M. S. T. G. M.'H. M. S. 



1 1 
6 

5 

4 
7 



00 

•20 
40 

00 



9 

T2 

t6 



20 37 

55 
9 20 
7 30 
13 7 

15 o 

16 45 

1 45 
5 3o 
30 o 



27 
29 
29 
29 

25 

24 
22 
19 

17 
'3 



45 
3* 
34 
03 
o 

5 

30 
30 

J 7 
23 



[o 53 58 
12 o o 
9 5 5 

35 50 

44 10 
55 22 

j 1 58 

39 14 
57 28 
26 56 



The time of the 

Tranfitus. 
of the Sun. 414 2 18 
of Mercury, jj o 1 10 



The Diameter in 
the Parallel. 
34 30 o 
o 17 30 



The Diameter in 
a great Circle. 
43 00 



From this Obfervation he had the Declination of 
Mercury in refpeftoF the Parallel through the Center 
of the Sun,and thence its abfolute Declination from the 
Equator, fuppofing the place of the Sun according to 
Hecker, and the obliquity of the Ecliptick, 23, 30' the 
right Afcenfion alfo of 2 appeared by the difference 
of time between the Traniit of 2 and the Weft limb 
of the Sun by the fame meridian. Then from the De- 
clination and right Afcenfion of 9 given by Trigono- 
metrical Calculation, he found out the Longitude and 
Latitude of it in every Obfervation, and the time of 
itstruc Conjunction. 




Therefore the time of the true conjunction of the 
Sun and Mercury at Avignon, was Nov. 7. Hor. 2. 
Min. 39. Sec. 14. Afternoon. 

To this he hath adjoyned thisenfuing Table, to fhew 
how much the Heavens do differ from the Aftronomi- 
cal Tables. 



Tempm datum ex Tabulis 
Novemb. 

D.H. M. 

RudoIphinisReyo « 

neri. f 7 

Calculis Heckeri. 
Lansbergianis. 
Philolaicis Bullialdi 
Ricciolinisjuxta 

,calculum. 
R. admodum Patris' 
Bonifa. Societatis 
Jefu. 



7 

6 



6 

1 

4 



9 
12 

18 



Differentia ab obfer- 

v&ta con)unUione. 
D. H. M. 

o 7 24 exceflus. 



exceffus. 
defedtus. 
excefius. 



o 5 9 
o 23 27 

3 39 



>7 8 17 o 7 38 exceffus. 



Vp9* 






C 73 ] 

Thefe Obfervations are delineated in the 23. Figure, 

Vpon this Ohfenationl find in the twenty 
third fournal de Scavans of the Year 
1 6jj.Mr.Ca[fmi made theJe%efleBions« 

THat having compared this Gbfervation of 
MonGeur GaUet , of 1677. with that of 
Mr. GaJJendm, of 163 1. the fame day of the year, to 
wit the feventh of November, he found that the Lati- 
tudes of 5 at its leaving the Difc of the Sun, de- 
termined by thefe two Aftronoraers were equal, even 
to the fixth part of a minute. And by confequence 
that £ was both in the one and the other Obfervation 
at the fame diftance from its North node, and that it 
traced in the Difc of the Sun an equal line : And for 
that £ was here at the like diftance from its Apoge 5 
as the Sun was alfo pretty near, the fwifthefs of its ap- 
parent motion in the Sun was equal. By the Obferva- 
tion of Mr. Gal/et it is found eonfiderably more flow 
than that which Mr. Gajfendvs hath f uppofed from the 
Rudolphin Tables of which he made ufe for the deter- 
mining of it, not having been able to make Gbfervation 
immediately by reafon of the Clouds. He believes 
then that 9 (pent more then five hours in running 
through the Difc of the Sun, fince by the Obfervation of 
Mr. Gallet, it hath fpent $ hours and 35 minutes, which 
may ferve for an Advertifement for determining more 
exactly the time of the true conjunction of 9 with the 
© in the year 1631. 

The fame equality of Latitude at kercury's leaving 
the Sun (hews that the Sun was equally diftant from 
the Node of Mercury at the time of thefe two Obfer- 
vations. And as the Sun was more advanced in that 
of this year from 63 to 64 minutes, than in that of 
the year 163 1, So it follows that the feptentrional 

L Node 



I 74 ] 
Node of 3 is advanced from 6% to 64 minutes in the 
fpace of 46 years, as precifely as by the Rudolphin 
Tables, which agree alfo exaftly intheEpochas of the 
Nodes: a matter ofnofmall Importance in Afrrono- 
my, which hath not a little difficulty to determine with 
precifenefs the Nodes of the Planets and their mo- 
tions. 

But having compared the obfervation of Mr. Galley 

with that of Mr. Hevelim , in 1661. which hap- 
ned the third of May, in a place of the Zodiac oppo- 
fite to that of this year, he hath found the feptentrion- 
al Node of $ lefs advanced than the Meridional was in 
the preceding Obfervation 5 fothat if the Nodes of 2 
in regard of the Sun are precifely oppofite the one ta 
the other, it appears that they have gone backward 
fince the year 1661. as do thofe of the Moon , and by 
confequence their motion is fometimes dire£r,fometimes 
retrograde : But if their motion is fuppofed uniform, 
it will follow that the Line of the Nodes of 9 doth 
not pafs at all through the center of the Sun , but that 
it is removed from it towards the feptentrional limit 
about a two hundredth part of the Semidiameter of 
the Orb of Mercury. 

Thus far this knowing and accurate Aftronomer 
Monfieur Caffim , who we hear hath fince farther dif- 
courfed concerning this matter, which we hope to pro- 
cure fo foon as he (hall make it publick} and to add 
fome other curious Obfervations made by other hands, 
I have as yet been able to procure but one more 3 but 
that is one fo considerable, that it will excite the skilful 
Aftronomers anew to ply their Calculations,to fee what 
the comparing of this with the reft will produce 5 
which as they come to my hands, I defign to pubhCh, as 
I (hall alfo fomewhat of my own Obfervations there- 
upon : and therefore I omit to make any refk&ions at 
prefent. This Letter is of Mr. Eclmmd Hally, now re- 
dding at St. He/e^, directed to Sir Jonas Moore, Sur- 
veyor of his Ma jellies Ordnance 3 a perlon to whom 

the 



C 75 1 
the Learned world is very much obliged for his patro- 
nizing and promoting thefe Coelefti-al enquiries 5 who 
hath not been (paring of his own pains and purfe in 
providing the beft apparatus of inftruments and other 
conveniences for fuch Obfervations the world ever had ; 
from whom we may with goodreafon hope a great ad- 
vancement towards the perfecting thereof. 




St. Helena , J\(ovemk zi. i6jj. 

Onored Sir , Ton may with reafon wonder that I 
JhouUlfo long be negligent to write to your Worfhip, 
to give yon an account of my proceedings jince my departure 
from you, feeing that in thebnfinefe I am now engaged upon, 
the Honorable Sir Jofeph Williamfon, his Majefiies Prin- 
cipal Secretary of State, and your felf are my only Patrons s 
hut I have not been unmindful of my Duty in this parti cu- 
lar-> only 1 delayed , that what I fen t you might not be aU 
together inconfiderable. I hoped Jiill that we might have 
fome clear weather when the Sun came near our Zenith, 
that fo I might give you an account that I had near handf- 
nifhed the Catalogue of the Southern Stars , which is my 
principal concern^ but fuch hath been my iU fortune , that 
the Horizon of this Ifland is almofb always covered with a 
Cloud, which fometimes for fome weeks together hath hid 
the Stars from m, and when it is clear , is offo fmall con- 
tinuance, that we cannot take any number of Obfervations at 
once 5 fothat now, when I expelled to be returning, I have 
net fihijloed above half my intended workj> and almoft de- 
fpair to accompli fh what you ought to expe^from me. IwiU 
yet try two or three months more, and if if continue in tht 
fame confiitntion, I Ji hall then, I hope be excuj able if in that 
time I cannot make an end. However it will be a great 
grief to befo farfrujiratedinmyfrji undertaking : I have 
notwjlhfianding had the opportunity of obferving theingrefs 

L 2 and 



L 76 ] 

andegrefsof S <?» f&? o, i*>fe£ compared with the Ufa 
Obfervations made in England, will give a demonstration 
of the Suns Parallax , »>&VA 'hitherto was never proved, 
hut by probable arguments. Likewife I havefeen thofe two 
Eclipfes, one of the Sun, the other of the Moon in May loft, 
both which I Jend you, but the mighty winds, and extra- 
ordinary fwift motion of the Clouds kindred the exaB- 
nefs of the Obfervations. That of the Moon may help for the 
difference of our Meridians , which is about 7 degrees to 
the Wejiwards of London : but it may more curioujly be 
found by Mercury Tub Sole. There are three Stars of the 
fir ft {Magnitude that- never appear in England , but none 
near the South Pole of any brightnefs , except one of the 
third Magnitude, which is about ten degrees difi ant from 
it. The two NubecuU called by the S ay lor 1 the Magel- 
Janick Clouds, are both of them exa&ly lik$ the whitenefs 
of the milky way lying within the Antartick. Circle - y they 
arefmall, and in the Moon fhine, fcarce perceptible 3 yetfn 
the dark, the bigger is very notable. I need not relate unto 
you the temperature of the Weather for heat and cold here in 
the Torrid Zone, you your felf having long fince had expe- 
rience of a Latitude little different : only this Ifiall cer- 
tify ou, that ever fince I came to this lfland,we have had no 
weather that is hotter than the Summer of England is or- 
dinarily. Mr. Clark is a perfon wonderfully ajjijiant to 
me, in whofe company all the good fortune I have had this 
Voyage confijieth, to me all other things having been crojs : 
neverthelejs Idefpair not of his Honors and your Worjhips 
favour, which alone is fufficien.t to encourage me to bear 
with patience thefe dif appointments, and expeft fome fitter 
opportunity. 

I am your Worfhips mod: obliged 
Servant, and true Honorer, 

Edmund Halley, 



Qftobris 






L77l 

St. Helena, Latitude Auftralis, 1 5. 5 5« 
Anno 1677. 

Oftobris 28. die mane # apparuit intra &* 

h. m. s-.. 

g- 26 17 Pars aliqua corporis V ii intrajjet Solent 
decern gradus a nadir ad dextram circiter. 

% 27 30 Formabat unguium contaUus lotus $ 
fcilicet. intus 

2 38 39 Limbus qii proximus dijjiti h limbo 
Selis Jui Diametro. 

2 40 8 Limbus K Mi tetigit limbum '. 

2 41 g Centrum £ e#/# e S0& %ograd. circi- 
ter a Nadir ad dextram. 

2 41 54 © limbus integer faBus* 

Longitudo & Latitudo trium Siellarum illuftrium 
pope polum auflrinum. 

"Long* Latit. 

Canopus 11 3 ® 75 49 

Centauri pes 25 24 m 4 2 22 ; 
Akamar* ,10 31 X 59 ^t* 



Br 



•. 1, 



The Teriod of the ^ewhtion of Jupiter 
upon it Axis ; Verified by new Obferva* 
tions made by Monfieur Cafllni : 

BxtraBedmt of the Journal de Scavam* 



TH E Globe of Jupiter , whofe Revolution about 
its Axis was determined by the Obfervations of 
Monfieur Cajjim, in the Year 
This Revolution of the body of 1 66 5 . to be Q hour S , and < 6 

?d5^t"d ft ptbXa minutes, isasitwerea watch 

in the firft Tranfaftion , which for yifibly pointing the hours 

was a considerable time before nrtc \ m ; ni1f . PQ fn u n if f t, p p nrf .u 

it was difcovered by Monfieur ana mmm ^ s to na . lf ™ e fcartn 

Cafmi j but we are obliged to at Once | lO that It IheWS the 

him for the perfecting the The- fame time to all under the fame 

ory, as we are alio for many 0- «. .-.,. j ,. rr 

ther rare Difcoveries and ex- Meridian, and a different time 
cellent improvements in Aftro- to different Meridians,accord- 
nomy. ^ -^ a§ ^y differ j n L or] g^ 

tude. 
It hath for an Index of its motion one principal fpor, 
which is very neatly diftinguifhed from the reft of its 
furface, and feems from its figure and fituation to have 
fomerefemblancetotheCafpian Sea of the Terraque- 
ous Globe. By the help of good Glaffesitmay befeen 
paffing the under Hemifphere of it , from the Eaft to 
the Weft, with a velocity fo fenfible , that one may de- 
termine to one or two minutes , the time that it comes 
to the middle of the Difc , which is the place the mod 
fit for eftablifhing of the Epochas, and for finding the 
difference of Longitude.There may be a great number of 
fach Revolutions obferved , fince in one year of 365 

days 



101 

days there are made 8B2 Revolutions. But it dotfi 
not appear in every year, but as if it were fome kind 
of Marifh which is dried at certain times , and fo diC- 
appears during two or 3000 Revolutions 5 and after it 
hath remained thus imperceptible for fome years, it re- 
turns again to its former Gate. After it had been ob- 
ferved the laii fix months of the year 166$. and fome 
months of 1666. it became invifible till the beginning 
of the year 1672. then being returned to its former ap- 
pearance, Moniieur Cajjini compared the intervals of 
the fix years , and limited the revolution to be made in 
9 hours, 5 5 minutes, 5 1 feconds, and continuing his Ob- 
servations to the end of the year 1674. ! he found by 
thefe two years that it was too flow by two feconds 
and a half: fo that it appeared to be in 9 hours, 55 mi- 
nutes, 5^ feconds. 

This fpot hath been invifible in 1675. and 1&76, du- 
ring which fpace there happened other very confider- 
able changes in the body of Jupiter 5 for the clear inter- 
face which was between the two dark belts of Jupiter 
was feparated into many little parts, in the manner like 
fomanylflands} as if the two obfeure belts had been 
two great Rivers broken one into the other , and had 
left thefe parts which appeared like Iflands, which yet 
were at laft all effaced, and the two dark belts, and 
the interjacent fpace at length all coalefced into one 
large belt. But after the coming of Jupiter out of the 
Rays of the Sun in the year 1677. the belts again took 
their form, and fituation which they had heretofore $ 
to wit, the.fame which is defcribed in the 24 figure. 
The principal fpot appeared anew after the beginning 
of July laft. Monfieur Cajfmi found this fpot in the 
middle of Jupiter the night after the eighth of the faid 
months at 13 minutes after on© at nighty and hath hi- 
therto ever fince obferved it at the hours proper to its 
revolution. Having compared many Obfervations of 
this year with as many others made the fame days of 
theyeari66s. for avoiding the fcruples which may a- 



C 80 3 

,rife from the inequality of times, he hath found by the 
intervals of twelve years that thofe revolutions compa- 
led the one with the other, complete themfelves in 9 
hours, 5 5 minutes, 52 feconds, and 5 or 6 thirds. And 
l>ecaufe that in the years 1672, 1673. they appeared 
more flow by 2 feconds and a half, during the time that 
Jupiter was in its greateft elevation from the Sun. 
Monfieur CaJJwi inclines to fuppofe that thefe revoluti- 
ons have fome little inequality depending on the vari- 
ation of the diftance of V from the 0, and that they 
are a little flower when # is more removed, and fbmc- 
what fatter when nearer approached that body 5 the 
fame which feveral great Aftronomers have fuppofed to 
happen to the Diurnal Revolutions of the Earth in the 
Copernican Hypothefis. 

In this account he hath feparated the inequality 
which doth refult from the variation of the two equa- 
tions of Jupiter (as he hath explained in divers Letters 
in 1665.) the which may amount to one half hour, be- 
fides the inequality of natural days, which according 
to his Hypothefis may amount to 1 6 minutes. 

For the rinding then of the return of the principal 
fpot to the middle of # for many years to half an hour 
•-or thereabout, there needs nothing but adding (till the 
time of the period to the Epoche of the 8. of July, 
1677. and for the rinding precifely, even to fome mi- 
nutes,the two inequalities of Jupiter muft be obferved 
according to the following Rule. 

Differentiate inter medium locum Jovk & appar:ntzm 
convert e in temp us dando (tngulk gradibus min. ij. hoc 
tempus adde tempori rejiitutionis macula fupputato , (i lo- 
cus apparens Jovis exceferit medium ; fubtrake vero ft de- 
fecerit a medio. v 

We have then the mean time of the return of the 
fpot, and to get the apparent time the,equation of days 
according to the method of Monfieur Cajjini (of which 
a Table is inferted in the Ephemerides of Monfieur Fla- 
minio de Mezzavachi) muft be madeufe of 

MI- 



c«o 



MICROSCOPIVM: 

O R, 

Some new Difcoveries made with and 
concerning Microfcopes* 

Ji Letter of the Ingeniom and Inquifitive Mr. Leeuwen- 
hoeck of Delft, fent to the Secretary of the Royal So- 
ciety, OUoher 5. 1677. 

IN this Letter after the Relation of many curious 
Obfervations made with his Microfcope , he adds, 
c By fome of my former Letters I have related what an 
innumerable company of little Animalcules, I have 

* difcovered in waters , of the truth of which affirma- 
c tions, that I might fatisfie the Illuftrious Philofophers 
c of your Society, I have here fent the Teftimonials of 
c eight credible perfons$ fome* of which affirm they 
c have feeni 0000, others 30000, others 45000 little 
c living Creatures, in a quantity of water as big as a 

* grain of Millet (92 of which go to the making up the 
*bignefsof a green Pea, or the quantity of a natural 
6 drop of waterj in the defiring of which Teftimonials 
6 1 made it my requeft that they would only juftifie 
c ("that they might be within compafsj half the number 
c that they believed each of them law in the water, and 
'even fo the number of thofe little creatures that would 
fi thereby be proved to be in one drop of water would 
c be fo great, that it would exceed belief. Now where- 
as by my Letter of the yxKotO&oher^ 1676. 1 affirmed 

* that there were more than 1 000000 living Creatures 
'-contained in one drop of Pepper-water. I fhould not 

M have 



C 8 2 3 

have varied from the truth of it, if lhad afTerted that 
c there were 80000005 for if according to forae of the 

* included teftimonials there might be found in a quan- 
' tity of water as big as a millet teed no lefs than 45000 
c animalcules. It would follow that in an ordinary drop 
6i of this water there would be no lefs than 4140000 

* living creatures, which number if doubled will make 
€ 8280000 living Creatures feen in the quantity of one 
5 drop of water,: which quantity I can with truth af- 
4 firm I have difcerned. 

c This exceeds belief. But I do affirm, that if a larger 

4 grain of fand were broken into 8000000 of equal 
*parts,one of thefe would not exceed the bignefsof one 

5 of thofe little creatures 5 which being underftood, it 

* will not feem fo incredible to believe that there may 
*befogreata number in the quantity of one drop ol 
s water*.. 

Upon the perufalof thisLetter,being extremely de- 
firous to examine this matter farther , and to be afcer- 
tained by ocular infpe&ion as well as from teftimoni- 
als*. I put in order fuch remainders as I had of my for- 
mer Microfcopes (having by reafon of a weaknefs in 
my fight omitted theufe of them for many yearsj and 
fteeped fome black pepper ki River water, but exami* 
ning that water about two or three days after , I could 
not by any means difcover any of thofe little creatures 
mentioned in the aforefaid Letter : though I had made 
ufe of fmall glafs canes drawn hollow for that purpofe, 
and of a Microfcope that I was certain would difcover 
things much (mailer than fuch as the aforefaidMr.Lem*?- 
enhoec\h2id. affirmed thefe creatures to be 5 but whe- 
ther it were that the light was not convenient ("the rea- 
fon of which I (hall {hew by and by)having looked only 
againft the clear sky,or that they were not yet generated, 
which I rather fuppofe, I could not difcover any. I con- 
cluded therefore either that my Microfcope was not (b 
good as that he made, ufe of , or that the time of the 

year 



year (which was in November) was not fo fit for fuch 
generations, or elfe that there might be fbmewhat af- 
cribed to the difference of places } as that Holland 
might be more proper for the production of fuch little 
creatures than England. I omitted therefore farther 
to look after them , for about five or iix days , when 
finding it a warm day, I examined again the faid wa- 
tery and then much to wonder I difcovered vaft mul- 
titudes of thofe exceeding fmall creatures , which Mr. 
Leeiwenhoec\ had def cribed 5 and upon making ufe of 
other lights and glaffes, as I (hall by and by (hew, I hot 
only magnified thofe I had thus difcovered to a very 
great bignefs, but I difcovered many other forts very 
much frnaller than thofe I firft faw, and fome of thefe fb 
exceeding fmall, that millions of millions might be con- 
tained in one drop of water. I was very much furpri- 
zed at thisfo wonderful afpe&acle, having never leen 
any living creature comparable to thefe for fmallnefs : 
nor could I indeed imagine that nature had afforded 
inftances of fo exceedingly minute animal produ&ions. 
But nature is not to be limited by our narrow •appre- 
henfions , future improvements of glaiTes may yet fur- 
ther enlighten our underftanding, and ocular infpedi- 
on may demonftrate that which as yet we may think 
too extravagant either to feign or fuppofe. 

Of this, AlaterDifcoveryof Mr. Leeurvenhoec\does 
feem to give good probabilities % for by a Letter of his 
fince fent ("the which is hereunto -annexed} it appears 
he hath difcovered a certain fort of Eels in Pepper- 
water, which are not in breadth above one thoulandth 
part of the breadth of a hair 5 and not above a hun- 
dredth part of the length of a vinegar Eel. 



M 2 Mr. Leeuw- 



LH1 
Mr. Leeuwenlioeclcs Second Letter. 

SI R, c Yours of the thirtieth o? November I received 
c not till January, whereby understanding the kind 
^reception of my former by the R. S. I here return my 
6 acknowledgment to that illuftrious Company for their 
^ great civility: but I wonder that in your Letter I find 
€ no mention made of my Obfervationsof thefecondof 
c December, St. No. which makes me doubt whether the 
6 fame came to your hands. 

c Since you affureme that what I fend of this nature 
fi will be acceptable to the renowned Society, I have ad* 
^ventured again to fend you fome of my farther Enqui- 
ries, to be communicated to that learned Philofophical 
Company. Since I wrote of the Blood of Eels , and 
c of young Eels , J have not been idle to view Blood, 
6 but especially my own, which for fome time I have m- 
6 defatigably examined, after that I had put it into all 
6 conceivable motions. Among which Obfervations I 
6 well faw that the globuli of my own blood took the 
« fame figure which I formerly mentioned, that the Glo- 
bules of the blood of Eels appeared of to the eye : 
c upon feeing which I doubted again at the caufe of the 
c fmart which the blood of the Eelscaufesin the eye. 

6 Thefe my many times repeated Obfervationsof my 
c own blood I made to no other end, than if it were.pof- 
s fible, to obferve the parts out of which the Globules 
6 of the blood confided : With obferving this, I found 
c the globulous blood much more pliable than I did imar 
* gine the fame, before. I have at fevera] times bended 
c thefe Globules before my eyes , that they were three 
'times as long as broad, without breaking the Veficule 
< of them : and befides J faw that the Globules of blood 
c in pafijng by and through one another, did, by reafon 
4 of their pi iablenefi receive many forts of figures, and 
'aoming thence, into a larger pkce 5 they recovered their 

former 



I HI 

•former globulofity which was a very great pleafure 

* to obferve : and withal , that the Globules of blood 

* coming many together , and growing cold thereby, 
6 came to unite , and liade a matter very fmooth, 

* wherein there were no ^iore parts diftincl: to be taken 
c notice of, much after the fame manner as if we fup- 
'pofeda Difh filled wjth balls of wax fet over a fire, 
c by which they wo)*lcl quickly be melted together,, and 
c united into one aiafs $ by which uniting of the Glo* 
6 bules, I concluded this to be the reafon of the acei- 
c dent which is called the cold fire , and of that alfo 
c which caufes the hands or fingers to be loft by cold': 

* but Heave this to others. And I did very clearly alfo 
c difcover that there were fix other fmaller Globules of 
6 blood contained within each of the former and lar- 
ger Globulous Veficles: and withal, I took much 
«• pains to obferve the number of the fame very fmall 
'globules, out of which the greater Globules do corr- 
c fift : that at laft I ftrongly imagined, that every of the 
«- greater Globules confifted of fix fmaller Globules, no 
6 lefs pliable than the aforefaid : for oftentimes I law 
'very clearly how the fmall Globules joyned and ada=- 
' pted themfelves according to the figure the Veficle 
6 - or larger Globule ftretehed at length had taken, being 

* themfelves ftretehed after the fame manner : and thus 
'made one of the larger Globules ftretcht out , to ap^ 

* pear by the lefler within it ftretehed alfo with it, 
c as if it confifted of long threads. Moreover, I 
'put the greater Globules into fo violent a motion, that 
'their Veficles bur ft in pieces, and then the lefler Glo* 
^ bules appeared plainly to be fcattered. This firft 
6 Globule I can fee as plainly and great, as withthena- 
£ ked eye one (hould look upon the eggs or (pawn of a 

«-Cod-fifli. 

c About nine or ten years fir/ce Dr. Graff opened in 
€ my prefence the vein of a Dog, and let out fo much 
1 blood that the Dog grew faint 3 then he opened the 
6 Artery of another Dog , and by, a pipe transfufed the 

M 3 bloods 



€ blood of this fecond into the firft, whereby the firft 
* was recovered,the fecond was Faint.Then the faid Do- 
c dor inje&ed back into the Artery of the fecond , a 
c quantity of Cows milk, fuppofing thereby to preferve 
c the fecond dog alive, faying, milk was blood : but 
c no fboner was the milk put into the artery , but the 
4 dog died. And whereas 'tis commonly laid that milk 
6 is Blood , therefore I (hall relate of what parts the 
c Milk confifts, fb far as I have hitherto difcovered. I 
'have faid heretofore that the Milk doth confift of 
'Globules fwimming in a thin clear watery matter 
6 which we call Whey : but as the great Globuli of 
6 Blood are all of the famebignefs, fb in the Milk they 
c are quite differing, being of as many fizes and magni- 
4 tudes as we can imagine , between the fmalleft land, 
4 and a barley corn $ all of them being as clear as Cry- 
6 ftal 5 fave only that through and between the fame 
4 drive fome irregular particles for the moft part roun- 
4 ded : thefe had a fatty fiibftance , which I imagined 
6 to be the latter : their irregularity I imagined came 

* from the impreffion of the encompaffing Globules 
6 made on them, in which pofture they grew cold. 

c Viewing the aforefaid differences of the Milk GIo- 
'bules, I fuppofed that the Milk veflels have no 
c other parts included but the matter out of which they 
c are all made 3 and that the fame matter, fb long as in- 
c eluded in the veflels, conftfted of one uniform matter, 
c fb that one could not diflinguifh parts 3 and that the 
c fame veflels difcharging this uniform matter into other 
c veflels, containing a fubftance of a quite differing na- 
c ture, which I fuppofeto be the Whey, comes to be 
' feparated into thefe Globules of fb differing magni- 

* tudes. This may be reprefented by having two vef- 

4 fels filled, the one with Fat, reprefenting Whey 5 the 

* other with Quickfilver, refembling the uniform mat- 

* ter of the Milk : thefe blended together, the Quick- 

5 filver will be feparated into fmall Globules of differing 
4 magnitudes, and kept diftinft by the fat. 

Or 



C*7l 

€ Or further, it may be explained by a diffolution of 
e fome gums in Spirit of Wine , a drop of which being 
c put into rain water (which I compare to Whey J the 
fi Gum becomes feparated immediately into an incredi- 
6 ble numbei-bf fmall clear Globules , which makes it 
€ appear alfo as white as Milk it felf: and thence Ifup- 
c pofe that the whitenefs of Milk hath the fame caufe. 

c I have been often minded by fome, that flefti was 
c nothing elfe but clodded blood 3 yet for all my en- 
c deavours I was never able to find the firft particles of 
c blood in the fibers of the flefli, but only fuch as are 
c contained in the firft Globules. 

c The laft Summer being fickly for fome weeks, I 
c voided much Flegm , which was green, tough, and 
c acid in the throat, which yet continues 5; but nothing 
e near fo much as before : and fome of it which I void- 
c ed;in the morning was of fo heavy a matter, that it 
c funk in the water: the ponderosity of it I found to 

5 proceed from its not being filled with airy bubbles, 
c which moft Flegms are mixed with. By this means I 

* obferved my Flegm very often , and found it to con- 

6 fift of tough (limy moifture, mixt with many Globulesi 
c and the tougher the Flegm was , the greater was the 
« quantity of Globules 5 and from them alfo proceed- 
c ed the green colour of it. All thefe Globules were of 
& one and the fame bignefs with the firft Globules of 
c the blood 3 and indeed the blood is of the fame 
£ make, but only of a different colour: for as I ob- 
c ferved the greater blood Globules to confift of fix 
4 lelTer, fo here I could fee them more plain 3 only they 
£ feemed more (lender and tender than in the blood : 
'the reafon whereof I fuppofe to be that the veficules of 
c the Flegm Globules had already received fome kind 
s of corruption : befides, there was mixt with the tough 
c part of the Flegm great quantity of very thin cuti- 

* cles : and in the fame manner as I have heretofore ex- 
plained how our cuticle is fupplied underneath, as the 
6 upper part is rubbed off in feurf, fo I fuppofe the in- 

nerv 



[S3] 
6 ner cuticles of the gullet afperaartcrta, and other ve£ 
c fels are taken off by the Flegm, There drove alfo, 
c through the Flegm fome other particles , which from 
• their fmallnefs I could not affign them a figure, but I 
c conceived them rather cubical than round. I did Iaft 
fi Summer (hut up fome Caterpillers tofpinWebs, and 
6 within thefe few days I broke fome of thefe Webs, 
■* when from each of them came out a flie , which from 
6 the cold were very weak, and were unable to ftand 5 
6 by which I conceive that thofe which came not out in 
c the latter part of the year , remain the whole Winter 
c in their Webs, till the warmth makes them come out. 
€ I was pleafed to underftand that your felf and the 
c Society hadfeen inib finall a quautiy of water ^s a 
c fand, fo great a number of Creatures 5 as alfo , that I 
€ fhall be partaker of what you (hall obferve, which I 

* fliall with longing defire exped. I cannot but men- 
tion that that fmall fort of Creature which I hereto- 
c fore could give no defcription of, I now fee their fi- 
gure. And for thepleafure I take in the various plea- 
'fingfhapes, with their motions, which do now and 
c then appear in the water, I have the fourth of this 

* month, when it froze hard, taken a third part of beat- 
6 en pepper, and f of high rain water in a clean glafs 

* which Ifet the .firft night in my Bed-chamber; the next 
c day, the weather being milder, Ifet it in my Counting- 
'houfe, and in three times 24 hours difcovered fo 
'great a number, and fo unexpreffible fmall Creatures 
c that us hard to be conceived 3 and according to my 

* judgment , the moll: of them were much Ms than a 

* thoufandth part of the thicknefs of the hair of ones 
•'.head, and three or four times as long as thick 3 the 

* which made, with the hinder part of their body , oft- 
'timesfofwiftaprogrefs, as when we obferve a' Pike 
e (hooting through the water, and every (hoot was in 
'length moll: times about half a hairs breadth 5 the 

* other forts or kind of which were yet fmaller , whofe 
*lhape for brevity I omit 3 only I fhallfay, that oft- 
times 



C%1 

c times in pepper- water which hath flood fomewhat 
c long, among the very frnall Creatures , I have feen a 
c fort of (mall Eels which had their ftiapes and moti- 
c ons as perfect as great ones : thefe were to my 
c appearance a thoufand times thinner than the hair of 
c ones head, and that if 100 of thefe frnall Eels were 
c laid in length one behind another , the whole length 
c would not extend to the length of the Eel in vine- 
c gar : Whether you have alfo obferved thefe frnall 
c Creatures with your Microfcope, I (hall be glad to un- 
c derftand. I would willingly alfo be informed whether 
c my Letter of the fecond of December mentioned above 
'be come to your hands, and how thofe Obfervations 
c do pleafe the Gentlemen of your Society 3 and alfo 
* to underftand the receipt of this. 

The manner how the faid MY.Leeunpenh&eck^doih make 
thefe difcoveries, he doth as yet not think fit to impart* 
forreafbnsbeft known to himfelf^ and therefore I am 
not able to acquaint you with what it is: but as to the 
ways I have made ufe of, I here freely difcover that all 
fuch perfons as have a defireto make any enquiries in- 
to Nature this way, may be the better inabled Co to do. 
Firft, for the manner of holding the liquor, foasto 
examine it by the Microfcope, I find that the way pre- 
ferred by Mr. "Leeumnhoech^ is to include the fame in a 
very fine pipe of glafs , and then to view it by 
the help of the Microfcope 3 for by placing that at a 
duediftance, whatever is contained in the faid liquor 
will moft eafily bedifcovered : The liquor will moft 
eafily infinuate it felf into the cavity of the faid pipe 9 
if the end thereof only be juft put within the li- 
quor. This as it is exceedingly convenient for many 
trials, fo is it not very difficult to prepare 3 but be- 
caufe every one is not intruded how to proceed in 
this matter, and it may caufe him more trouble than 
needs to procure them, I will here defcribe the way \ 
and fo much the rather, becaufe the fame apparatus will 

N ferve 



ferve for the preparing of Mierofcopes: as I (hall af- 
terwards fhew. 

Provide then a box made of tin, with a flat bottom, 
and upright on all fides 5 let this have fixed within it to 
the bottom a fmall piece of tin, hollowed like a ridg 
tile, fo that thewiekof the Lamp may lie and reft up- 
on it, and let the Tin-man fix on it a cover of tin , fo 
that there may be only left one part of the aforefaid 
box open, to wit, where the bent tin piece and the 
wiekdolieand come above the fides: this cover may 
be turned back on its hinges when there is occafion to 
raife the wiek, or put in more oyl, &c. but for the moft 
part ought to lie flat and covered , for whilft it is ufing, 
it is neceflary to keep the flame from fpreading too 
much, and taking fire all over. This box muft ftand 
within another box of tin, made large enough to con- 
tain it 5.. the ufe of which is to keep the former Lamp 
Box from fowling the board or table on which it 
(lands : This ftandsupon a board about one foot fquare, 
into which is faftned a ftandard or ftick upright, cleft 
fo as to pinch and hold the fodering pipe between its 
clefts, which may be faftned with a (crew, or a flipping 
ring 5 through which pipe, blowing with your breath, 
the flame will be darted forward with great fwiftnefs 
and brightnefs : if then into this flame you hold a fmall 
piece of a glafs pipe, made of white glafs , ("for green 
glafs, or coarfer glafs will not be melted eafily in this 
flame) and keep it turning round between your fingers 
and thumbs, you (hall find that the flame will in a very 
fhort time melt the middle part of the laid pipe 5 fo 
that if you remove it out of the flame, and draw your 
hands one from another, you may eafily draw the for- 
mer pipe into a very fmall fize , which will yet remain 
hollow, though drawn never fo (mail. The beft Oyl 
for this purpofe is good clean Sallat Oyl, or Oyl Olive 5 
but high rectified Spirit of Wine is yet better , and 
cleanlier, but much more chargeable 5 and for moft ufes 
the, Oyl Olive will ferve. This I have fet down , be- 

caufe 



C 91 1 

caufe many who are far off in the Country cannot hav£ 
the convenience of going to a Lamp-blower as ok as 
they have occafion for fuch pipes} which if they pro- 
vide themfelves with fmall white glafs pipes from the 
Potters , they may accommodate themfelves withal, 
though they have nothing but a large candle, and a to- 
bacco-pipe, inftead of the aforefaid apparatus, though 
not altogether fo conveniently. But I would rather 
advife them to have a Lamp made, which moft Tin-men 
know how to fit and prepare 3 and fo it will not need 
much more defcription. 

But this way of Mr. Leenwenhoecks* of holding the li- 
quors in fmall glafs pipes, though it be exceedingly in- 
genious, and very convenient for many examinations, 
yet for divers others 'tis not fo well accommodated as 
this which I contrived my felf for my own trials, at 
lead: for thofe Microfcopes I make ufe of^ what it may 
be for thofe which Mr. Leeuwenhoeck^ ufes I know not. 

I take then inftead of a glafs pipe a very thin plate 
of Mufcovy glafs, this ferves inftead of the moveable 
plate which is usually put upon the pedeftal of Micro- 
fcopes 3 but becaufe the common pedeftal hitherto 
made ufe of in Microfcopes is generally not fo conve- 
nient for trials of this nature, I lay thofe by, and in- 
ftead thereof I fix into the bottom of the Tube of the 
Microfcope, a cylindrical jod of Brafs or Iron. Upon 
this a little focket is made to Aide to and fro 5 and by 
means of a pretty ftiff fpring , will ftand faft in any 
place. This hath faftned to it a joynted arm of three or 
four joynts, and at the end a plate about the bignefs of 
a half crown, with a hole in the middle of it about 
three quarters of an inch wide 5 upon this plate I lay 
the Mufcovy glafs , and upon that I fpread a very little 
of the liquor to be examined 3 then looking againft 
the flame of a Candle, or a Lamp, or a fmall reflexion 
of the Sun from a globular body 3 all fuch parts of 
the liquor as have differing refraftion will tnanifeftly 
appear. By this means I examined the water in which 
™ J N2 I had 



C 9* ] 
I had ftceped the pepper I formerly mentioned 5 
and as if I had been looking upon a Sea , I fa w infinite 
of fmall living Creatures fwimming and playing up and 
downdnit, a thing indeed very wonderful to behold. 

If the flame of the candle were dire&ly before the 
Microfcope, then all thofe little Creatures appeared 
perfectly definU by a black line , and the bodies of 
them fomewhat darker than the water 5 but if the can- 
dle were removed a little out of the axis of vifion, all 
thofe little Creatures appeared likefo many fmall pearls, 
or little bubbles of air, and the liquor in which they 
fwimmed appeared dark * but when the water began 
to dry off, the bending of the fuperficies of the liquor 
over their hackstand over the tops of other fmall motes 
which were in the water made a confufed appearance^ 
which fome not ufed to thefe kind of examinations* 
took to be quite differing things from what they were 
really 3 and the appearances here are fo very ftrange, 
that to one not well accuftomed to the phenomena of 
fluids of differing figures and refra&ions, the examina- 
tions of fubftances this way will be very apt to mif-in- 
form, rather than indraft him ,5 efpecially of fuch fub- 
ftances as are not perfectly fluid, and will not readily 
and naturally fmooth their own fuperficies , fuch as 
Tallow, concreted Oyls, Marrow, Brains, Fat, infpifla- 
ted juyces, &c. for if thofe fubftances be fo examined 
by lpreading them upon this plate , and be looked up- 
on againft the candle, or other finall defined light , all 
the inequalities left on the furface by the fpreading do 
by the refra&ions of the rays of light render fuch odd 
appearances, that they will eafily deceive theexaminar 
tor, and make him to conceive that to be in the tex- 
ture of the part which isreally no where but in the 
make of the fuperficies of it. This therefore as ano- 
ther great inconvenience to be met with in Microfcopi- 
cal Obfervations, I prevent by thefe enfuing methods : 
Firft, all fuch bodies as Fat, Oyl, Brains, Rhobs,jFW, 
tough concreted Flegm, and the like., whofe furfaces 



are 



C 93 3 

arc irregular, and ought to be reduced to fmoothneis 
before they can be well examined, I order in this man- 
ner: Firft, I provide a very clear and thin piece of 
looking-glafs plate very fmooth and plain on both fides, 
and clean from foulnefs : upon the furface of this I lay 
fomeofthofe fubftances I laft mentioned, then with 
fuch another piece of Looking-glafs plate laid upon 
the faid fubftance I prefs it fo thin as not only to make 
thefurfaces of it very fmooth , but alfo to make the 
fubftance of it very thin 5 becaufe otherwife , if the 
fubftance be pretty thick, asfuppofe as thick as*a piece 
of ^/re paper, if it be a whitifti fubftance, the mul- 
titudes of parts lying one upon another in fuch a thick- 
nefs, do fo confound the fight, that none of them all 
can be diftinftly feen : but if by fqueezing the faid plates 
hard, and clofe together , it be reduced to a twentieth 
part perhaps of that thicknefs , the fubftance may be 
well looked through, and the conftituent parts may 
be very plainly difcovered. Thus alfo 'tis very vifible 
in the Globules of milk and blood, difcovered by the 
ingenious Mr. Leeum^hoeck, for when either of thofe 
fubftances are thick, the multitude of thofe little Glo- 
bules confound and thicken the liquor fo as one can- 
not perceive any thing until it be run very thin 5 for 
then all the remaining Globules with their motions may 
very diftmcrly be apprehended. This therefore is an 
expedient by which thoufand 3 of fubftances may be 
examined 5 and therefore the more fit to be communis 
cated, that there may be the greater number of obfer- 
vers well accommodated for fuch trials. Thefe plates 
therefore may be contrived fo as to be pinched toge- 
ther by the help of fcrews, and a frame , that thereby 
they may be forced the clofer and the evener together, 
as there (hall be occafion$ and may be kept firm and 
fteady in that pofture, and then, that it mayfome 
ways or other be conveniently faftned to the former 
plate, foasto be moved this way or that way fteadily* 
as there .(hall be occafion. 

N 3 But 



C 941 
But there are other fubftances which none of thefe 
ways I have yet mentioned will examine , and thofe 
are fuch parts of animal or vegetable bodies as have a 
peculiar form, figure, or (hape, out of which if it be 
put , the principal thing looked after is deftroyed : 
fuch are the Nerves , Mufcles , Tendons , Ligaments, 
Membranes, Glanduks, Parenchymas, &c. of the bo- 
dy of Animals, and the Pulps, Piths, Woods, Barks, 
Leaves, Flowers, &c. of Vegetables. Some of thefe 
which are not made by diffe&ion or feparation from 
other parts may be viewed alone 5 but there are others 
which cannot be well examined unlefs they be made to 
fwi-m in a liquor proper and convenient for them : as 
for inftance , the parts of flefh, mufcles and tendons : 
for if you view the fibres of a mufcle encompaffed on- 
ly with the air, you cannot difcover the fmall parts out 
of wfyichitismade: but if the fame be put into a li- 
quor^ as water, ©r very clear oyl , you may clearly fee 
fuch i fabrick as is truly very admirable, and &ch as 
none hitherto hath discovered that ever I could meet 
with 3 of which more hereafter, when I fhew the true 
mechanical fabrick thereof, and what caufes its motion. 
Thus if you view a thred of a Ligament, you fhall 
plainly fee it to be made up of an infinite company of 
exceeding fmall threads fmooth and round , lying clofe 
together 5 each of which threads is not above a four 
hundredth part of the bignefs of a hair : for compa- 
ring thofe of Beef with a hair of my head, which was 
very fine and fmall, viz. about a 640. part of an inch, I 
found the Diameter thereof to be more than twenty 
times the Diameter of thefe threads 5 fo that no lefs 
than 163 millions, befides 84othoufands of thefe muft 
be in a ligament one inch fquare. I fhall not here en- 
large upon the admirable contrivance of Nature in this 
particular, nor fay any thing farther of the reafon of 
the greater ftrength of the fame fubftance drawn into 
fmaller than into greater threads 5 but only this in ge- 
neral, that the mechanical operations of thefe minute 

bodies 



[95] 
bodies arc quite differing from thofe of bodies of great- 
er bulk, and the want of confidering this one thing 
hath been the caufe of very great abfurdities in the 
Hypothefes of fome of our more eminent modern Phi- 
lofophers : For he that imagines the aftions of thefe 
leffer bodies the fame with thofe of the larger 
and tradable bodies , will indeed make but Art- 
fiotles wooden hand at beft. This put me in mind 
likewife of advertifing the Experimenter that he pro- 
vide himfelf with inftruments , by which 5 to ftretch 
and pull in pieces any fubftance whilft the fame 
is yet in view of the Microfcope , of which there 
may be many which any one will eafily contrive, when 
he hath this hint given him of the ufefulnefs thereof in 
the examination of the texture of feveral fubftances 5 
as of Tendons, Nerves, Mufcles, &c. thofe I have made 
ufe of were made to open like a pair of Tobacco 
Tongues, by two angular plates of thin brafs rivetted 
together, which by pinching the oppofite end, would 
either open or (hut at the other, as I had occafion. 
Thefe having a part extended between the two tops, 
were fixt at a due diftance from the objed-glafs that 
the body extended between them might be diftin&ly 
feen $. then with my finger fqueezing together the op- 
pofite ends , the other ends opened , by which means 
how the parts ftretched and ihrunk might be plainly 
difcovered. Now as this is of ufe for fome kind of 
fubftances, fo the two glafs plates are for others , and 
particularly for fqueezing of feveral fubftances be- 
tween them, fo as to break them in pieces, as thofe lit- 
tle Creatures in pepper- water, or the Globules in blood, 
milk, flegm, &c. whereby the parts within them may 
yet farther be enquired into, as Mr. Leeuwenhoesk. I find 
hath done by his lateft Obfervations. Whether he makes 
ufe of this way, or feme other, I know not. 

Having thus given a defcription of the appurtenan- 
ts, it remains that I come to the defcription of the Mi- 
cro^ 



[96] 
crofcope it felf , which is the principal inftrument, and 
without which all the reft are infignificant. 

TheMicrofcopes then I defign here to defcribe , arc 
only of two kinds, either fingle or double. 

The fingle Microfcope I calf that which confifteth 
only of one glafs , though it have a double refra&ing 
fiiperficies$ and the double one I call that which is 
compounded of two glaffes, though it hath for the moft 
part a quadruple refraction of the Rays. 

The fingle Microfcope then confifteth of one finall 
lens (b faftened into a cell, that the eye may come con- 
veniently to look through the middle part or Axfr of 
it 5 of thefe there are various forts,as double Convexes, 
or plain Convexes, or perfectly fpherical. 

I ihall not need to defcribe the common lenfes which 
are every where made ufeof for thispurpofe, being 
plano-convexes of Spheres about half an inch Diame- 
ter, fave only this , that 'tis beft to turn the plain fide 
towards the object, and the convex to the eye ; nor 
fhall I fay much concerning thole double Convex Glafc 
fes , there being no great difficulty in the making or 
ufing of them 3 but that the fmaller the Iphere is in 
which they are made, the nearer do they bring the ob- 
ject to the eye 5 and confequently the more is the object 
magnified, and the better and truer they are polifht in 
the Tool, the more clear and diftincl: doth the object 
appear, but to make any of a Sphere le(s than A of 
an inch in Diameter is exceeding difficult , by reafon 
that the glafs becomes too fmall to be tradable 3 and 
'tis very difficult to find a cement that will hold it faft 
whilft it be completed 3 and when 'tis polifht, 'tis ex- 
ceeding difficult to handle and put into its cell : be- 
fides, I have found theule of them orlenfive to my eye, 
and to have much ftrained and weakened the fight, 
which was the reafon why I omitted to make ufe of 
them, though in truth they do make the objeft appear 
much more clear and diftincl: , and magnifie as much as 
the double Microfcopes : nay, to thofe whole eyes can 



C 97 1 

well endure it, 'tis poffible with a fingle Microfcope to 
make difcoveries much better than with a double one^ 
becaufe the colours which do much difturb the clear 
vifion in double Microfcopes is clearly avoided and pre- 
vented in the fingle. The (ingle Microfcope therefore 
which I (hall here defcribe, as it is exceeding eafie to 
make,fo is it much more tradable than the double Con- 
vex glaffes made the common way by working, them in 
a hollow Hemifphere with water and fand 5 for thofe, 
fuppofing them made with all the accuratenefs imagin- 
able, will be far (hort from being fo well polifht as 
thefe 5 and wanting the ftem or handle which thefe 
have, they are infinitely troublefome to remove, or 
place, or to cleanfe when there (hall be oecafion. 

Take then a fmall rod of the cleared and cleaneft 
glafs you can procure,free if poffiblefrom blebbs,fands 9 
or veins 5 then by melting it in the flame of a Lamp 
made with Spirit of Wine, or the cleaneft and pureft 
Sallet Oy3, draw it out into exceeding fine and fmall 
threads 3 then take a fmall piece of thefe threads, and 
in the fame flame of the aforefaid Lamp melt the end of 
it, till you perceive it to run into a little ball or glo- 
bule of the bignelsdefired 5 then fuffer it to cool, and 
handling it by the aforefaid thread of glafs, which is as 
it were a handle to it, fix it with a little wax upon the 
fide of a thin plate of Brafs, Silver, or the like, that the 
middle of it may lie dire&ly over the middle of a fmall 
hole pricked through the faid thin plate with a needle •: 
then holding this plate clofe to the eye, look through 
the faid little hole, and thereby you may alfo fee very 
clearly through the aforefaid Globule , fixed with wax 
on the fide that is from the eye : if then either by a lit- 
tle joynted arm, or by a little foft wax , and a needle,, 
or a thin plateof Mufcovy glafs, you fix the objeft you 
would examine 5 fo that it may beat a due diftance from 
the faid little Globule, you will perceive the minute 
parts thereof very diftin&.The/^^ofafphere looked 
on by the naked eye, is about half the radius of the 

O fphere 



C 98 3 

fphere, without the fuperficies of it 5 but this is varied 
much by the age of the eye that looks through^ , by 
the imagination alfo of the perfon , and by the differ- 
ing fpecifique reflation of the glafs made ufe of 

By this means I have prodigioufly magnified fome 
frpall bodies, infomuch that I have been able to fee and 
diftinguifh the particles of bodies , not only a million 
of times fmaller than a vifible point, but even to make 
thofe vifible, whereof a million of millions of them 
would hardly make the bulk of the fmalleft vifible fand 5 
fo prodigioufly do thefe exceeding little Globules of 
glafs inlarge the profpeft of humane fight into the more 
private recedes of nature. 

If the things to be viewed be liquors , they may be 
included either in thofe little pipes of Mr Luuwenhoeck^ 
B newly mentioned, or elfe they may be put upon ex- 
ceeding thin plates of Mufcovy glafs or Selenites, and 
the other fide of the plate may be made to touch the 
Globule, or at lead: be fixed at fuch diftance, as may 
make the parts of the liquor diftind : If you make ufe 
of a Looking-glals plate to fpread the liquor upon you 
Would examine, you may turn the liquor towards the 
Globule,^ and you may therein eafily fee all the parts 
very diftin&iy , without at all hurting the proipeft by 
the interpolation of thzMnjcovy glafs 5 which though 
it be exceeding clear , efpecially if the plates be very 
thin, yet hath it fome flaws, and fome opacoufneffes in 
it, which do fome what cloud the profped. 

If further, you would have a Microfcope with one 
finglerefraclion 5 and confequently capable of the great- 
ell: clearnefs and brightnefs that any one kind of Mi- 
cro'fcopes can poffibly be imagined fufceptible of, when 
you have fixt one of thefe little Globules as I have di~ 
te&ed, and fpread a little of the liquor upon a piece 
of Looking-glafs plate, then apply thefaid plate With 
the liquor, next to the Globule, and gently move it 
clofe to the Globule, till the liquor touch j which done, 
}ou will find the liquor prelently to adhere to the 

ClOr 



L99l 
Globule, and ftill to adhere to it though you move it 
back again a little 5 by which means, this liquor being 
of a fpecifique refra&ion, not much differing from glafs, 
the fecond refraftion is quite taken off, and little or 
none left but that of the convex fide of the Globule 
next the eye 5 by which means as much of the incon- 
venience of refra&ion as is poffible is removed, and 
that by the eafieft and moft pra&icable expedient that 
can be defired. I could add various other ways of 
making thefe Globular bodies both of glafs and other 
fubftanc.es which will yet farther advance our profpedt 
into nature, and are pleafant to admiration 5 but thofe I 
(hall yetreferve till I fee what effects the publifbing of 
thefe may produce , and to the end to excite other 
perfons to be inquifitive i nto this matter : for let me af- 
faire them, very much more may yet be done by a way 
I know, than by this I have here publifhed. And I 
confefs I have very often wondered that no farther im- 
provement had been made of this Principle, iince I 
publiflit it in the year 1664. in the 20. page of my Pre- 
face to Micrograph a. : for though lbme other reafons 
difcouraged me from prolecuting thofe enquiries, 
yet I hoped that others might long before this have 
carried it much farther. 

The only inconvenience in thefe kinds of Micro- 
fcopes, is, that theobje&is neceilarily brought fo near 
the glafs, that none but fuch as are tranfparent , and to 
be viewed by a through light are capable of examina- 
tion by them : fuch therefore are to be examined by the 
double Microfcope 3 which, as it is abundantly more 
tradable, fb doth it much lefs ftrainthe eye 3 and from 
the eafinefe of its ufe, when well fitted , is much more 
pleafant: and if ordered as it ought, will magnifie as 
much more than the common ones hitherto made, as 
thofe did more than the naked eye. 

Both thefe Microfcopes I have directed Mr.Chriftopher 
Cock,, in Long- Acre^ how toprepare,that fuch as will not 
trouble themfelves in the making of them, may know 

O 2 where 



where to be accommodated with fuch as are good. 
And of the improvement of this kind of Micro- 
fcope, I fee no limits, efpecially as to the augmenting 
the vifible appearance of fuch obje&s as are capable of 
enduring the increafe of light 5 for fince 'tis demonftra- 
ble that light may be augmented upon any one objecl 
fufceptible to any given degree, and that by the double 
Microfcope the image can be augmented to any affign- 
ed magnitude , what but the difficulty of making all 
things correfpondentfhould limit the power of fuch an 
rn.ftrument. Now the making of this double Micro- 
fcope, though it be fomewhat more difficult than of the 
lingle one, yet the tra&ablenefs thereof when well fit- 
ted, and its eafinefs to be eleanfed,^ and applied to ufe, 
makes amends for the extraordinary charge , efpecially 
the fituation of the object:, which being capable of 
any reaforiable diflance from the objecl: glafs, fo as to 
be fit for examination, makes it very defirable. Now 
as in all other mechanical contrivances , that is bed 
which is plained , and moll: fimple : fo is it in this, 
wherein nothing more is required, but two piano Con- 
vex glaffes, the one for the objecl:- glafs, and the other 
for the eye-glafs : the lefs the fpheres of the glaffes be, 
the more do they magnifie the objecl: j and the thinner 
and clearer the fubftance of them be, and the more ex- 
acllyfliaped, and the brighter they are polifht, the 
clearer do they reprefent it - y and the longer the glaffes 
.are diftant from each other, the more is the image mag- 
nified, ceteris paribw^ though indeed the fame thing is 
performed by glades of very differing magnitudes, due 
proportions of all things about it being kept and oh- 
ferved; For if as the diflance of one objecl: from the 
objecl-glafsls to the diflance of another object from an- 
other objecl:-glafs, fothe diftanee of the firft image be 
to the diflance of the fecond image, the image in both 
muflbe equal': if therefore this image be viewed with 
equal: glafles- the image muft be equally magnified -at 
the bottom of the eye ? fo that in this w T ay the objecl: is 



capable of a double way of augmenting, viz. firft, the 
augmenting the figure in the Tube, by the fmallnefs of 
the objecVGlafs, and lengthof the Tube : and fecond- 
ly, by the augmenting that image in the bottom of the 
eye, and that is by the Eye-glals 5 give therefore light 
enough to the object, and you may inereafe the image 
at the bottom of the eye to what proportion you fhall 
defire. And by a way I (hall fhortly (hew, the objects 
may be perceived diftinft, defined, and colourlefs, as if 
feen by the naked eye. In a-llthefe ways the manner 
,of applying the light is very (ignificant, and provided 
it be very ftrong, the {mailer the point be it proceedeth 
from, the more diftin&ly doth it exhibit the difference 
of refraction in the tranfparent bodies viewed by it, and 
the plainer will their parts be difcovered: The light 
therefore of the Sun either reflected from a Spherical 
Convex body, or Spherical Concave body, the object 
being placed beyond the focus, or Refracted through 
a Concave or through a Convex,if the object be placed 
beyond the focus, do exceedingly well. But thefe with 
the help of a dark Room do yet better, the object 
being placed in a Table againft the Light, and all other 
Light fcreend from the Eye by the Dark Room. Much 
the fame thing is done by the Light of a Lamp or 
Candle in the Night, which is indeed the mofb'conve- 
nient Light, where Colour is not fo much looked after* 
Whileft this Difcourfe was Printing I cafuallymet 
with a Treatife of P. Cherubine^ Printed at Parity 
1677. Entituled, LA FISION P ERE AITE, 
on Us concows des deux axes de la Vifion en> unfceul point 
de V'objed^ Wherein the Author pretends amongft other 
things to have promoted Microfcopes extreamly by 
fo joyning two together, as through them to fee the 
fame objeS diftincl: with both the Eyes at once 6 and 
to fee a large -.object all at one view, by which he a£ 
firms to have difcovered fome miftakes and untruths 
in fome of thofe figures I have formerly publilhed in 
mj.. Micrography , But if he had pleated to have read 

O i the-. 



C 102 ] 

the Defcription as well as looked on the Figure, he 
might have been better informed than by his Preface 
he would feem to be. I deny not but that there are many 
failures in fome of thofe draughts, fome of my own and 
fome of the gravers committing. Humanum eft. But 
thofe which he charges for fuch are not, as hemight 
have feen if he had madeufe of better glaffes than thofe 
which he defcribes, for they are fo far fhor t of equalling 
thofe I ufe, that I can demonftrate from his own De- 
fcription of them, that thofe I made ufe of did magnifie 
* i Oooo times more than that with which he pretends to 
have made thefe great Difcoveries. Nor is it any thing 
more than common to fee as large an Area as he men- 
tions, with a glafs that magnifies no more than his 
doth. But I could have (hewed him how he might 
fee the whole Creature at once, and yet much more 
magnifie than that which I have defcribed, nay though 
the Creature were twice as big, and that with one Eye 
only, which is much to be preferred before that with 
two. However I lhould be very glad to hear what 
Difcoveries he doth make with his binocular Micro- 
fcope more than was feen before. As alfo that he would 
pleafe to demonftrate the truth of Parallelogram pre- 
scribed for certain ufes, pag. of Dioptrique Ocu- 
laire,and in the Fourth Chapter of the Fourth Part of 
this Book. But to digrefs no farther from what I was 
deferibing. I mud add that with both thefe kinds of Mi- 
crofcopes have I examined feveral fubftances, as par- 
ticularly the fteepings of feveral grains and feeds in 
rain-water. And though I have not yet found any one 
tin&ure more prolific than this of Pepper 5 yet 'tis not 
the only tin&ure in which they do both breed and in- 
creafe.I have feen feveral forts in the fteeping of Wheat, 
Barly, Oats, Coffee, Annifeeds, Peafe, &c. fome not 
above a third part of a hair <in thicknefs , others not 
above the twentieth part of the breadth of a hair, and 
fome not more than a thirtieth part of that breadth^ (b 
that no lefs than 900 of thefe leaft mull: go to make an 

area 



[1033 

area as big as that of an hair cut tranfverfly, and 27000 
to make a Cylinder as big as the hair of ones head, and 
of equal height with the Diameter of that hair, which 
one may juft call a vifible point, and no more 5 few 
eyes feeing things diftin&ly much fmaller: Now the 
Diameter of a hair of my head being by examination 
found but the 640 part of an inch, it follows that no 
lefsthan 19200 or to ufe a round lumm about 2 0000 of 
them may lie in the length of an inch, and confequent- 
ly, that a circle an inch Diameter will be to the area 
ofoneof thefe cut tranfverfly as 40000000c to 1. four 
hundred millions to 1 and a Cylinder one inch Dia- 
meter ,and one inch high,will be to one of thefe mites,as 
8000000000000 to one, eight millions of millions to 
one. If therefore we compare the magnitude of one of 
thefe animals to the magnitude of other creatures living 
in the water,we (hall find that thefe will be found much 
fmaller in companion to the body of an ordinary 
Whale, than the body of the fame Whale will be to 
the body of the whole Earthy which may prove an 
argument for an anima mnndi perhaps to fome. But let 
every one make his own inferences , and believe his 
own eyes, for they will make the beft impreffion on 
his reafon and belief. Now if the Creature be fo ex- 
ceeding fmall, what muft we think of the Mufcles, 
Joynts, Bones, Shells, eK. certain it is, that the Me-- 
chanifm by which Nature performs the mufcular moti- 
on is exceedingly fmall and curious, and to the perfor- 
mance of every mufcular motion in greater Animals at 
lead, there are not fewer diftincl: parts concerned than 
many millions of millions, and thefe vifible , as I (hall 
hereafter fhew through a Microfcope 3 and thofe that 
conceive in the body of a mufcle, little more curiofity 
of mechanifm than in a rope of the fame bignefs^ have 
a very rude and falfe notion of it 3 and no wonder if 
they have recourfe to Spirits to make out the Pheno- 
mena : but of this hereafter more. 

Eurther, I have examined the conftitution of Blood, 



[104] 

Milk,Flegm, &c. and found thern much the fame with 
what Mr. Leeuwenhoek^ has declared. A little fat laid 
upon the glafs plate whiM warm, melts, and becomes 
tranfparent, but obferved in a convenient pofture a- 
gainft the light of a candle, &c. till it congeals, and 
{brinks, make a pleafant fluid, and (hews how confi- 
derably a fluid and folid body do vary, and may give 
us a good hint to conjecture at the reaibn of the fwel- 
ling and greater lightnefs of Ice than of Water. The 
firft beginnings alfo of the (hooting or cryftallifing of 
Sugar into re&angularparallelipipeds, Alum, Salt, Vi- 
triol, &c. are ftrangely furprizing and inftru&ive , I 
could enumerate multitudes of thefe. 

But (that I may not detain the Reader toolong in 
the perufal of thefe anatomical deferiptions of the mi- 
nute and invifible parts of animal fubftancesj to eafe 
both his eyes and imagination I fhall proceed to ac- 
quaint him with fome Anatomical Obfervations more 
fenfible , and which do feem more nearly to concern 
us. And thofe are contained in the enfuing Difcourfe, 
being 



A Re- 



A Relation communicated to me in a Letter by thai ingeni- 
ous and experienced Chirurgion Mr, James Young of 
Plimouth , in the beginning of January loft, of the fatal 

- Symptoms caufed by a Bullet fw allowed into the Lungs. 

SI R, In the beginning of April, 1674. one Mv. An- 
thony Williamjon of Lifcard in Corneal, aged about 
65 years, of a brisk, firm habit, became ("after a too li- 
beral drinking of Cyder J affii&ed with the Colick, of 
which in four days he cured himfelf,by (wallowing two 
Musket Bullets, and receiving fome Carminative Cly- 
fters. On the 12. of the fame month, his pain returning 
fome what fmarter than before, he attempted to fvvallow 
three Piftol Shot, and fuppofing it the eafieft way , he 
lay on his back, and threw them all at once into his 
throat} where they choaking , had almoft ftrangled 
him 5 conftraining him to vomit, &c. When they were 
paft down, he became feized immediately with a violent 
Cough, Wheafing, pain in the left fide of his Breaft, a 
great noife in refpiratton , more efpecially after a fit of 
Coughing^ for then his Breaft would hifs, like the fuck- 
ing of a Pump , when the Air defcends through the 
boxes. 

Thefe accidents fo fuddenly occurring, without any 
manifeft caufe, did much furprize him, and the more, 
becaufe he was naturally of a found breaft 5 the Co- 
lick was cured by Clvfters,Potions of Manna, olamygj. 
&c. and two of the Shot were foon ejected, ex ano, 
and maugre the other accidents,he became indifferently 
well, and able to walk about houfe. 

Five or fix weeks after this, thofe fymptom s became 
more fierce, depaupering his fpirits, proftrating his ap- 
petite, difquieting his deep with dreams,a Dyfpncea, and 
rutling violent Cougfya ftraitnefsand load in his Breaft 
kept him in bed, extenuated his body (which without 
help of Milk Clyfters, was coftivcj) he frequently fain- 
ted with fweats, and a tickling fleepinefs in both legs. 

P Un- 



Under the tyranny of this legion of fymptoms, our 
Weftern Apollo*. Dr. Bidgood of Exeter was confulted, 
who affirmed them all to be caufed by the remaining 
Bullet, which paffing through the Larjnxjn 'as fallen in- 
to one of the branches of the Trachea. , where it would 
abide, in defpight of any endeavours to ejecl: it : yet 
to alleviate the violence of the accidents , he directed 
totheufe of emollient Eclegmas, temperate Cordials 
&c, by help of which j and fome other propitious' 
circumftances, he not only recovered his legs, becoming 
able to walk, and ride a fmall Journey, but alfo confum- 
mated Marriage with a young woman of 2 5 — who af- 
terward brought him two Children, w hereof one is now 
alive, and very lufty^ and was feven months gone with 
a third, when he died : the more wonderful if the wo- 
man were juft to him (of which there appeareth norea- 
fon to doubt) becaufe a very little motion would foin- 
ereafe his difficulty of breathing, as to make him faint. 

After Matrimony he had divers lucid Intervals , at 
times would be very brisk, and at others very languid, 
and faint, like a dying man : he continually expectora- 
ted, fometimes grumous coagulated Blood, otherwhiles 
very recent 3 now purulent foetid matter, then laudable 
pus. His natural averfion to Medicine caufed him to re- 
ject what was ad vifed by Dr.Bzdgood, Dr. Lower ^ Dr» 
Sprage, &c. faving a few of the more flight mixtures: 
And although Sack had been formerly very familiar to 
him,he was now forced to fhunit 5 andall ftrong Drinks, 
becaufe they would infallibly produce a Cardialgia , a 
pulfant throbbing of the Heart, and labouring°in his 
Breaft: the firftof thefe perhaps proceeded from his 
Conftitution, which inclined to Cholera but the lat- 
ter undoubtedly ,from the errervefcency, and warm mo- 
tion, to which it enforced the Blood, which the obftru- 
cYion and pfeffure the Bullet occafionedin the Pnenma* 
tkk. organs, could not peaceably admit of: wherefore 
he refolutely Rxtd to fmall Drink , and fhunned , as 
muchaspoffible, all ..evitable Exercife, faving that of 

his 



[i©7] 
his hands, which he frequently employed in making 
Net-work. 

In the Year 1676. he applied himfelf to our ingeni- 
ous and learned Country-man, Dr Mayovp oFBath, who 
agreed with Dr. Bidgood , that the remaining Bullet 
lodging in the Lungs, was the occafion of all thofe ill 
fymptomes under which he laboured %, but feemed to 
drflent from his prefage,by hoping he might expe&orate 
it: to atchieve which , he dire&ed to have the body 
fufpended head downwards, and fumes of S tor ax, Ben- 
jamin, &c. to induce expulfrve Coughing,together with 
©oncuffions of the body,andall preceded with an open- 
ing courfe, to relax, and dilate the veffels of the Breaft 5 
all which were ufed to nopurpofe, lave to verifie Dr. 
Bidgoods Prognoftick, that no efflation , how violent 
foever, would be able to extrude it, and inhaunce the 
Patients defpair of being ever cured 3 from which time 
he never attempted it : fo that thofe fymptomes before 
mentioned, continuing until the Winter, and then gain- 
ing confiderably onhim,efpecially the H#mo$ty$s 9 &c* 
he languiihed till the ninth of December laft , and then 
died. 

The tenth Ditto (affifted by his Son-in-law) I open- 
ed the Thorax^ in prefence of two other Chirurgions 
of the place , together with divers perfons of Quality, 
whole curiofity led them to fee the examination 3 be- 
caufe the Bullets being there, was fo much doubted by 
many, and difputed as impoffible by others. In the dip 
fe&ion the following particulars wereobfervable 5 

The Body was extenuate and tabid, 

The right lobes of the Lungs were replete , found* 
and well coloured. 

The Serum in the Pericardium was almoft all abfu- 
med, 

The Heart ftrangely fhrivelled and very fmall. 

Under the Pericardium (the Body being fnpne) we 
found a lump of coagulated Blood, as big as a Pigeons 
Eggs near which lay alfo a fubftance, fhaped like an 

P 2 ©btufc 



[ io8 ] 
©btufe headed mufcle, having a Tendon-like tail,which 
infinuated to the Pendant Lobe : Its body was above 
an half inch thick. Its other dimensions and fhape ex- 
actly like that of the figure X, of which A fiieweth 
the head or upper end, B the tail , which in drawing 
out of the rotten Lungs (being alfo corrupted ) broke 
afunder. Its Texture Teemed fibrous , like that of the 
Kidneys, being white one half way through, the reft of 
a dark red : it was very foft and plum , having a firm 
fmooth tegument, and felt very much like a Sheeps kid- 



ney. 



The left Lobe of the Lungs was cadaverous , and 
hollow, by an abfcefs which had difcharged near a pint 
of very fetid and purulent matter, into that fide of the 
trunk where it lay immured up, by the adhefion of the 
Lungs on that fide, to the Pleura, which with the Dia- 
fhragm^ as far as the mattex extended,, was livid, and 
eroded. 

We examined this rotten part of the Lungs, with 
what exa&nefs and curiofity we were capable of, amidft 
fiich a. crowd as were prefent 5 and the more trouble- 
fome ftench of the Cadaver 5 and found though the 
whole Parenchyma were rotten, and no firmer than co- 
agulated Blood (with which it had very near refem- 
blance)yet the branches of the Trachea continued into 
it were uncorrupt, and found 3 nor in any of them could 
we find what we very confidently prefumed to be 
there, viz. the Bullet. 

Wherefore I refolved to feek it the way by which it 
mult have entred 5 and accordingly dividing the 
Trachea at its infertion to the Lungs , I thruft in a ben- 
ded Probe to the left branch, and there felt him, lying 
loofe about two inches, within it, which with my fin- 
gers I eafily exprelled at the divided end of the pipe: 
to do which, I laid it bare fo far as where the Bullet 
had lodged 5 and Iproteft, to my wonder, I found it 
not any way injured, or altered, by hardnefs, erofion, 
&c, though the Bullet had divers imgreffions from the 
Aater, The 






t *°9 3 

The fanguiferous veffels, though lacerated , and cut 
in the difie&ion, did yield little or no Blood, either 
fluid or coagulate. 

Thus far is true Hiftory, and matter of fad $ I muft 
now beg your pardon , if I prefume to give my fen(e, 
and apprehenfion of fome of thole Phenomena here 
related. 

The extenuation- of the body , the abfumption of 
the firum in the Heart-bag, and the contraction of the 
Heart, were the effects of the Tabes $ and that occa- 
fioned by the Bullets injuring the Lungs, and pecloral 
veflels. 

The lump of coagulate blood found under the Heart- 
bag was extravafate from the rotted veins, and arteries 
of the Lungs. 

That ftrange fubftance lodged between the Peri car- ' 
dium^ and the Bullet, was either a Polypus > and the ex- 
crefcenceof fome part, or it was generated by nature, 
and fubftituted for a cufhion to defend the Heart from 
injury, by fo uneafie a neighbour. That Polypufes have 
been found in the Heart, is affirmed by Nicolas Tulpius, 
Marcellm Malpighius G. Qarmrus y 8cc. but their fhape 
and texture differing vaftly from that of ours, giveth 
reafon to believe this to be none $ efpecially conflder- 
ing that they all excrefcing from the Heart , or fome 
carneous part, are infeparably united and radicated to 
their original, and arefpungy, whereas this was no- 
thing lefs, having no root, nor fo much as an adheiian 
any where, laving at the tail $ the fmall end of which, 
being rotted by the Lungs,, into which it continued, 
did eafily divide upon my endeavour to draw it out : 
the body of italfo lay loofe in the aforefaid interftice, 
andas eafily flipped out, as a Wqu^ox 3. Struma^ when 
the containing parts are opened* Its fubftance was not 
fungous, but of a foft firmnefs, like, a Kidney $ ; and in 
whatever circumftances it may refemble a Polypus, as 
k doth the figure of that of the Nofe, vide N. Tulpii 
oLmed.Ub,i>cbf. 26.yetit.alfo differs from all other ex-- 



[no] 
crefcences, befides, in what hath been mentioned, in 
that it was not rooted in any fiefhy, bony, or mufculous 
part 5 and fuch the Lungs are well known not to be : it 
muft therefore be the ftupendious effecT: of Natures in- 
duftry, and laid as a cufhion to defend the Heart, &c, 
Its compofition being Co delicately foft , and yet firm 
enough for fuch a purpofe: Its magnitude, fituation,c^r. 
concurring alfo to confirm this opinion concerning it 5 
befides which , I do almoft remember , and believe 
(though I cannot be pofitivej that the pulfantpain he 
had fo violently in his Breaft, toward the left fide, de- 
creafed gradatim^ from the time of the deglutition : i£ 
that be true, whatever the fubftance were , or its caufe, 
its effects were very propitious, manifefting nature to 
be , not only a diligent fupplier of her own defecls, 
but as induftrious to produce ftrange and unaccount- 
able relief^ in fuch emergencies as this before us : A re- 
fembling ftory we have from A Pareus^ lib. 8, cap. 1 5. 

The abfceft was without doubt from a Phlegmon of 
the Lungs 3 and becaufe for the moft part it was below, 
or beyond the Bullet , it proceeded rather from its ob- 
ftru&ing, and fo ftagnating the Blood, and recrements in 
that Lobe, than from extravafation. What occurred of 
the latter, was expectorated, or remained iri fuch Coa- 
-gulums as that found under the Heart. 

The caufe of the Bullets falling, rather into the left 
than the right Ramus of the Trachea , is obvious from 
the more fupine and direft figure thereof , correfpond- 
ing with the trunk, as the figure doth manifeft ; which 
consideration, together with the Bullets being loofe in 
the pipe, renders the unfuccefsfulnefs of Dr. Mayow's 
attempt very wonderful: I am inclined to believe it 
was fb, either for want of a more early trial, or a more 
skilful tryer , than him who was employed about it. 
The way was ingenioufly contrived, and (as the Do- 
dor himfelf told mej had been fuccefsfully experien- 
ced in the like occafion. Certainly , had not the di- 
ftance of the Doctors abode,and very important avoca- 
tions. 



C hi] 

tions, denied his perfonal affiftance ; or had any other 
perfon skilled in Anatomy, &c. been fubftituted, the 
Bullet from his own favourable (hape, and more propi- 
tious gravity, and particularly from the ftrong efflati- 
ons they provoked , together with the affiftant pofture 
of the body, would have been extruded. Had they 
infteadof hanging him perpendicular, made him incline 
a little to the right fide, to have made the left Ramus 
more prone 5 and at the fame time made him diftend 
the pipes by fucking in as much breath as they could 
contain , their other means might have been effectual 3 
which J am induced to prefume from the profperous 
effedrsofthe like attempt, and yet wanting many of 
their advantages^ I mean the reverfion of a Stone, when 
fticking,and not able,to pafs through the Urinary Chan- 
nels. Let any Phyficians ferioufly perpend the difficul- 
ty of this, with the advantages for the former, and 
they will juitifie my opinion. 

The erofion of the Pleura^ni Diaphragme^ was from 
the acidity of the matter , gnawing and corrupting 
them 5 for though the Irachea wonderfully efcaped 
fuch impreffions, the Bullet difcovered on its luperfi- 
cies, divers marks of erofion, which all- acids produce 
with much facility, upon the faceharous or (aline parts 
of Lead 5 as is to be feen by immerfing it in vinegar. 

And now Sir, to relieve your patience ("no lefsthan 
my own) perhaps already wearied with the prolixity 
of this Narrative, give me leave to conclude, with fug- 
gefting, that ram of a belief paving perufed mofl: of 
the publick accounts of this kind) that fcarcely a rarer 
accident, and accompanied with fitch flupendious cir- 
cumftances, hath occurred to the prefent age than this 3 
that an extraneous body, fo large, fo heavy, fo hard, 
fhould flip down that difficult, and unufual way of 
the Weafon, and abide fo long in the organs of refpira- 
tion, info aged a perfon, admitting after it fuch exer- 
cifes, as he performed, Riding, Marriage, &c. that na- 
ture fhould fo unaccountably provide fuch a pertinent 

fence; 



[II2J * 

knee againft injuries accidentally accruing, and that 
even the (mailed Ramifications otthe Trachea, though 
immerled in iuch a Cadaver, (hould be preferved from 
injury thereby. I am fure in the voluminous Gbfer- 
vations of Schenckius , Horjiius, Riverius, Bartholine, 
Burnet, Sec. nor among all the ftories in Mr. Oldenburg's 
Tranfac"tions. ) or the Mifcellanea Curiofa of the Leipfaic^ 
Doctors, hath it a Parallel. 

'this, and whatever is elfe contained -in this Hiftory, 
as my kok y t fubmit to the better fenfe, and reafon of 
the Learned , not prefuming to be pofitive in any 
thing, fave in affirming my felf, &e. 

JAMES YOVNG. 
P. S. 

For the plainer mxleirCtapding Where the Bullet 
lodged in the Wind-p*pe, I have drawn and fent you 
an exa£t figure of xhtTrachea, excarnificd} as its to be 
be found in Gerrard Blajjitts , Syntagma Anatomic um 
J.-Vefiingi. -See figure Yin the III. Table. 

C points to the Trachea divided under the Larynx. 

D the right Ramus of the Trachea. E the left. 

F the place where the Lung&adhered to the Pleura. 

g g g, &e. the extremities of tho(e branches of the 
Ajperaarteria, divaricated into the rotten Lobe. 

H the Bullet in the pipe where it was found. 



ERR ATA. 

Age i. line iy.foot.ip. 2.l6.joyned,y.B.Lzi.Cete 3 \).iiA.<),is diffufed^.u. 

1. 1 i.Foflor^.i 2.\>3 ^.within ibefpbtre of its a%ivity,y.i i.I.34.dele ^p.14. 
LS.ether, p.i ^.common fights, p.22.1.31. Ait^out, p.23.1.1 $.bm produced,?^. 
I.27. add fee fig. 4.p.z7 .I.5.0/ 'this orb, P.27.U1.1U, p. 28.1.27../^ figure, p.zp. 
U%,& perige, p.29 l.z$.B,B,£. ib 1 26, 27. H,H,I. p.? i.l.p/orCOP^Ofc^fcJs 28, 
■fa-earn of babies, p.35.1.29.add ^.^.p.38.1.28.fo get out of I.2.4. of finding the, 
p.46.1 qi.Baldwines y.^.l. 17. downwards (hall touchy. $4. ] .26.Scolopendra,p.6g 
l.uIt.S^^p.yi.l^.fbr 43 put 34, p.83.1.8.^ my wonder, p.93- J -5-t>loc ouc 
fir(l,^6,li^plano connexes y ^.ioi.l2zlor table put f^p.ioi.l.30.5^: 
Xiy.magnifiid^.tmparaleUogYam^^page 241, p.xo 4 .l.tf. for fluid put/"<?//d. 



••■• 




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H. ; i i • 



ill I \ w! 
•ill * 1 i! 







'i' / /'« \ i]i 



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1T.IM V: U \ 

^ !\ ! ti Vl ! 

$ hvi \i lit 

1 \ I -, \ -l \ I ' 

I 1 » i-' \ ' ; 



I 'I 






'/ 'i 'i 

/ f! /i 



7 / 




\HVN\ V!i;1/;/i/// 






Tab. I. 



Tab. Ill* 




Tab. m a / 




#*■* 



. z s 



Tab. "V* '' HypathesXi>Chr?'»ren,.Sc 



V 




% 




EC T 

De Tote mi a Reftimtiva* 




OR OF 




X 



ining the Power of Springing 

To which are added fome 

collect I 




ADefcription flfJDKPappins Wind-Fountain and Force-Pump, 

Mr .Young's Obfervation concerning natural Fountains. 

Some other Confederations concerning that Subjetf. 

Captain Sturmy'/ remarks of a Subterraneous Cave andCiflern* 

Mr.G. T .Obfervations made on the Pike of Teneriff, 1 674. 

Some Reflections and CcnjeUures - occasioned thereupon., 

A Relation of a late Eruption in the IJle of Palma. 



By %0 S E %^T EOOKE. $ 9 R,S. 



Pri 



LONDON, 

fozjolm Martyr PnntQX to the ^pyal 
at. the Bell in St. Pauls Church-Yard, 1678 




CO 

Totentia Reftitutiva, 

O R 

SPRING. 

He Theory of Springs, though 
attempted by divers eminent 
Mathematicians of this Age 
has hitherto not been Publifhed 
by any. It it now about eighteen 
years fince I firft found it out, 
but designing to apply it to fome 
particular, ufe, I omitted the 
publishing thereof. 

About three years fince His Majefty was pleafed to 
fee the Experiment that made out this Theory tried 
at White-Hall, as alfo my Spring Watch. 

About two years fince I printed this Theory ill an 
Anagram at the end of my Book of the Defcriptions of 
Heliofcopes,w2,.c eiiino s ssttu ujdeji^Jt tenjiojic 
vk^ That is, The Power of any Spring is in the fame 
proportion with the Tenfion thereof : That is, if one 
power ftretch or bend it one fpace, two will bend it 
two, and three will bend it three, and fo forward. 
Now as the Theory is very (hort, fo the way of try- 
ing it is very eafie. 

Take then a quantity of even-drawn Wire, either 
Steel, Iron, or Brafs, and coyl it on an even Cy- 
linder into a Helix of what length or number ofturns 
you pleafe, then turn the ends of the Wire into 
Loops, by one of which fufpend this coyl upon a 
nail, and by the other fuftain the weight that you 
would have to extend it, and hanging on feve^al 
Weights obferve exactly to what length each of the 
weights do extend it beyond the length that its own 
weight doth ftretch it to, and you fhall find that if 

B one 



CO 

one ounce, or one pound, or one certain weight 
doth lengthen it one line, or one inch, or one cer- 
tain length, then two ounces, two pounds, or two 
weights will extend it two lines, two inches, or 
two lengths 5 and three ounces, pounds, or weights, 
three lines, inches, or lengths 5 and fo forwards. And 
this is the Rule or Law of Nature, upon which all 
manner of Reftituent or Springing motion doth pro- 
ceed, whether it be of Rarefaction, or Extension, or 
Condensation and Compreffion. 

Or take a Watch Spring, and coyl it into a Spiral, 
£q as no part thereof may touch another, then pro- 
vide a very light wheel of Brafs, or the like, and Rx 
it on an arbor that hath twp fmall Pivots of Steel, 
upon which Pivot turn the edge of the faid Wheel 
very even and fmooth,, fo that a fmall filk may be 
coyled upon it 5 then put this Wheel into a Frame, fo 
that the Wheel may move very freely on its Pivots 5 
fatten the central end of the aforefaid Spring clofe to 
the Pivot hole or center of the frame in which the 
Arbor of the Wheel doth move, and the other end 
thereof to the Rim of the Wheel, then coyling a fine 
limber thread of filk upon the edge of the Wheel 
hang a fmall light fcaleat the end thereof fit to receive 
the weight that (hall be put thereinto 5 then fuffering 
the Wheel to ftand in its own pofitionby a little index 
faftned to the frame, and pointing to the Rim of the 
Wheel, make a mark with Ink, or the like, on that 
part of the Rim that the Index pointeth at 5 then put 
in a drachm weight into the fcale, arid fuffer the 
Wheel to fettle, and make another mark on the Rim 
where the Index doth point 5 then add a drachm more, 
and let the Wheel fettle again, and note with Ink, as 
before, the place of the Rim pointed at by the In- 
dex 5 then add a third drachm, and do as before, and 
fo a fourth, fifth, fixth, feventh, eighth, &c. fuffer- 
ing the Wheel to fettle, and marking the feveral 
places pointed at by the Index, then examine the 

Diftances 



Diftances of all thore marks, and comparing them 
together you (hall find that they will all be equal 
the one to the other, fo that if a drachm doth move 
the Wheel ten degrees, two drachms will move it 
twenty, and three thirty, and four Forty, and five 
fifty, and fo forwards. 

Or take a Wire firing of twenty, or thirty, or 
forty foot long, and fallen the upper part thereof to 
a nail, and to the other end faften a Scale to receive 
the weights: Then with a pair of ComparTes take the 
diftance of the bottom of the fcale from the ground 
or floor underneath, and fet down the faid diftance, 
then put in weights into the faid fcale in the fame 
manner as in the former trials, and meafure the feveral 
ftretchings of the faid firing, and fet them down. 
Then compare the feveral ftretchings of the faid 
ftring, and you will find that they will always bear 
the fame proportions one to the other that the weights 
do that made them. 

^ The fame will be found, if trial be made, with a 
piece of dry wood that will bend and return, if one 
end thereof be fi xj in a horizontal pofture, and to 
the other end be hanged weights to make it bend 
downwards. 

The manner of trying the fame thing upon a body 
of Air, whether it be for the rarefa&ion or for the 
compreflion thereof I did about fourteen years fince 
publifh in my Micrographia, and therefore I {hall 
not need to add any further defcription thereof. 

Each of thefe ways will be more plainly under- 
ftood by the explanations of the annexed figures. 

The firft whereof doth reprefent by A B thecoyl 
or helix of Wire, Cthe end of it, by which it is fu- 
fpended, D the other end thereof, by which a fmall 
Scale E is hanged, into which putting Weights 
asFCHIKLMN, fingly and feparately they being 
in proportion to one another as 12345678, the 
Spring will be thereby equally ftretcht to o,pfl,r,s&u^ 

B 2 that 



mm 

[41 

that is, if F firetckit fo as the bottom of the Scale 
defcend to 0, then G will make it defcend to p 9 
H to q 9 I to *y K to x, L to *, M to #, and N to v> y &c. 
So that x<? (hall be one (pace, xp, 2, x^ 3 3, xr, 4, 
x /, 5, x t y 6 r x u y 7, x »>, 8. 

The fecond figure reprefents a Watch Spring coy- 
led in a Spiral by C AB BB D, whofe end C is fixed 
to a pin or Axis immovable, into the end of which 
the Axis of a fmall light Wheel is inferted, upon 
which it moves 3 the end D is fixed to a pin in the 
Rim of the Wheel yyyy, upon which is coyled a 
"" fmall filk, to the end of which is fixed a Scale to re- 
ceive the weights. To the frame in which thele are 
contained is fixed the hand or Index z • then trying 
with the former weights put into the Scale E, you 
will find that if F put into the Scale E finks the bot- 
tom of it xtotf, then G will fink it top, and H to q y 
Itor, Ktoj, L to *,andz will point at 1,2,3,4,5,6,7,8 
on the Wheel. 

The trials with a ftraight wire, or a ftraight piece 
of wood laid Horizontal arc Co plain they need not 
an explication by figure, and the way of trying upon 
Air I have long fihce explained in my Micogra- 
■ghia. by figures. 

From all which it is very evident that the Rule or 
Law of Nature in every fpringing body is, that 
the force or power thereof to reftore it (elf to its na- 
tural polition is^always proportionate to theDiftance 
or (pace it is removed therefrom, whether it be by 
rarefadion, or reparation of its parts the one from the 
other, or by a Condenfation, or crowding of thofe 
parts nearer together. Nor is it obfervable in thefe 
bodys only, but in all other fpringy bodies whatfo- 
ever, whether Metal, Wood, Stones, baked Earths, 
Hair, Horns, Silk, Bones, Sinews, Glafs, and the like. 
Refped being had to the particular figures of the 
bodies bended, and the advantageous or difadvan- 
tagious ways of bending them. 



From this Principle it will be eafie to calculate 
the feveral ftrength of Bows, as of Long Bows or 
Crofs-Bows, whether they be made of Wood, Steel, 
Horns, Sinews, or the like. Asalfo of the Balifta ox 
Catapults ufed by the Ancients, which being once 
found, and Tables thereof calculated, I fhall anon 
{hew a way how to calculate the power they have 
in (hooting or carting of Arrows, Bullets, Stones, 
Granadoes, or the like. 

From thefe Principles aifo it will be eafie to calculate 
the proportionate ftrength of the fpring of a Watch 
upon the Fufey thereof, and confequently of adjuft* 
ing the Fufey to the Spring fo as to make it draw or 
move the Watch always with an equal force. 

From the fa me alfoit will be eafie to give the rea- 
fon of the Ifochrone motion of a Spring or extended 
firing, and of the uniform found produced by thole 
whofe Vibrations are quick enough to produce an 
audible found, as likewife the reafon of the founds, 
and their variations in all manner of fonorous or 
fpringing Bodies,of which more on another occafion. 

From this appears the reafon, as I fhall (hew by 
and by, why a Spring applied to the balance of a 
Watch doth make the Vibrations thereof equal, whe- 
ther they be greater or (mailer, one of which kind I 
fhewed to the right Honourable the Lord Vifcount- 
Brounker^ the Honourable Robert B^/eEfq 5 and Sir 
Robert Morey in the year 1660. in order to have got- 
ten Letters Patents for theufeand benefit thereof 

From this it will be eafie to make a Philofophical 
Scale to examine the weight of any body without 
putting in weights, which was that which I menti- 
oned at the end of my defcription of Hel-iofcopes, the 
ground of which was veiled under this Anagram, 
c ediinn oops ssttuu^ namely, 1)t pondus fie ten- 
Jio. The fabrick of which fee in the three firft figures. 
This Scale I contrived in order to examine the gra- 
vitation of bodies towards the Center of the Earth, 

B 3 viz»tQ- 



m 

viz. to examine whether bodies at a further diftance 
from the Center of the Earth did not lofe fcmewhat 
of their power or tendency towards it. And pro- 
pounded it as one of the Experiments to be tried at 
tjhe top of the Pike of Teneriff and attempted the 
lame at the top of the Tower of St. Pauls before the 
burning of it in the late great Fire 5 as alfo at the top 
and bottom of the Abby of St. Peters in Wejlminfler 
though thefe being by but (mall difbnees removed 
from the Surface, I was not able certainly to perceive 
any manifeft difference. I propounded the fame alfo to 
be tried at the bottom and feveral ftations of deep 
Mines 5 and D. Power did make ibme trials to that end, 
buthislnftruments not being good, nothing could be 
certainly concluded from them. 

Thefe are the Phenomena of Springs and fpringy 
bodies, which as they have not hitherto been by any 
that I know reduced to Rules, fb have all the attempts 
for the explications of the reafbn of their power, and 
of fpringinefs in general, been very inefficient. 

In the year 1660. I printed a little Trad, which I 
called, An Attempt for the explication of the Phenome- 
na, &c. of the rifing of water in the pores of very 
fmall Pipes, Filtres, a^c. And being unwilling then to 
publifh this Theory, as fuppofing it might be preju- 
dicial to my defign of Watches, which I was then 
procuring a Patent for, I only hinted the principle 
which I fuppofed to be the caufe of thefe Phenomena 
of fprings in the 3 1 page thereof in the Englifti Edi- 
tion, and in the 98 page of the Latine Edition, tran- 
flatedby M.Behem, and printed at Amflerdam, 1662. 
But referred the further Explication thereof till fbme 
other opportunity. 

The Principles I then mentioned I called by the 
names of Congruity and Incongruity of bodies. And 
promifed a further explanation of what I thereby 
meant on fome other occafion. I fhall here only ex- 
plain fo much of it as concerns the explication of this 
preftnt Phenomenon. By 



If) 

By Congmity and Incongruity then I uriderftand no« 
thing elfe but an agreement or difagreement of Bo. 
dys as to their Magnitudes and motions. 

Thofe Bodies then I fuppofe congruous whofe 
particles have the fame Magnitude, and the fame de- 
gree of Velocity, or elfe an harmonical proportion 
of Magnitude, and harmonical degree of Velocity. 
And thofe I fuppofe incongruous which have neither 
the fame Magnitude, nor the fame degree of Velocity, 
nor an harmonical proportion of Magnitude nor of 
Velocity. 

I fuppofe then the fenfible Univerfe to confift of 
body and motion. 

By Body I mean fbmewhat receptive and commu- 
nicative of motion or progreffion* Nor can I have any 
other Idea thereof, for neither Extention nor Quan- 
tity, hardnefs nor foftnefs, fluidity nor~fixednefs, Rare- 
faction nor Denfation are the proprieties of Body, 
but of Motion or fbmewhat moved. 

By Motion I underftand nothing but a power or 
tendency progreffive of Body according to feveral de- 
grees of Velocity. 

Thefe two do always counterbalance each other in 
all the efTefts, appearances, and operations of Na- 
ture, and therefore it is not impoffible but that they 
may be one and the fame 5 for a little body with great 
motion is equivalent to a great body with little moti- 
on as to all its fenfible effects in Nature. 

I do further fuppofe then that all things in the llni** 
verfe that become the obje&s of our fenfes are com- 
pounded of thefe two ( which we will for the pre- 
fent fuppofe diftinft: effences, though poffibly they 
may be found hereafter to be only differing concepti- 
ons of one and the fame effence)namely,B^,and Moti- 
on. And that there is no one fenfible Particle of matter 
but owes the greateft part of its fenfible Exteiafion to 
Motion whatever part thereof it ows to Body accord* 
iag to the common notion thereof : Which is, that 



Body is fomewhat that doth perfectly fill a determi- 
nate quantity of (pace or extenfion fo as neceffarily 
to exclude all other bodies from being comprehended 
within the fame Dimenfions. 

1 do therefore define a fenfible Body to be a de- 
terminate Space or Extenfion defended from being 
penetrated by another, by a power from within. 

To make this the more intelligible, Imagine a 
very thin plate of Iron, or the like, a foot fquare, 
to be moved with a Vibrative motion forwards and 
backwards the flat ways the length of a foot with 
fo fwift a motion as not to permit any other bo- 
dy to enter into that fpace within whkh it Vi- 
brates, this will compote" fuch aneffenceas I call in 
my fenfe a Cubick foot of fenfible Body, which dif- 
fers from the common notion of Body as this fpace 
of a Cubick foot thus defended by this Vibrating plate 
doth from a Cubick foot of Iron, or the like, through- 
out folid. The Particles therefore that compofe all 
bodies I do fuppofe to owe the greateft part of their 
fenfible or potential Extenfion to a Vibrative motion. 

This Vibrative motion I do not fuppofe inherent or 
infeparable from the Particles of body, but communi- 
cated by Impulfes given from other bodies in thellni- 
verfe. This only I fuppofe, that the Magnitude or 
bulk of the body doth make it receptive of this or- 
that peculiar motion that is communicated, and not 
of any other. That is, every Particle of matter ac- 
cording to its determinate or prefent Magnitude is 
receptive of this or that peculiar motion and no 
other, fo that Magnitude and receptivity of motion 
feems the fame thing: To explain this by a fimilitude or 
example. Suppofe a number of mufical ftrings,as ABC 
D E, &c. tuned to certain tones,and a like number of 
other firings, as a,b,c,d,e, 8cc. tuned to the fame founds 
refpe&ively, A fhall be receptive of the motion of a 9 
but not of that of b, c, nor d$ in like manner B fhall be 
receptive of the motion of b 7 but not of the motion 

of 



t9l 
of #,<? or d. And Co of the reft. This is that which 
I call Congruity and Incongruity. 

Now as we find that mufical firings will be moved 
by Unifons and Eighths,and other harmonious chords, 
though not in the fame degree 5 fo do I fuppofe that 
the p articles of matter will be moved principally by 
fuch motions as are Unifons, as I may call them, or of 
equal Velocity with their motions, and by other har- 
monious motions in a lefs degree. 

I do further fuppofe, A fubtil matter that incom- 
1 pafleth and pervades all other bodies, which is the 
Menflruum in which they fwim which maintains and 
continues all fuch bodies in their motion, and which 
is the medium that conveys all Homogenious or Har- 
monica! motions from body to body. 

Further I tuppofe, that all fuch particles of matter 
as are of a like nature, when notfeparafed by others 
of a differing nature will remain together, and 
ftrengthen the common Vibration of them all againft 
the differing Vibrations of the ambient bodies. 

According to this Notion I fuppofe the whole 
Univerfe and all the particles thereof to be in a con- 
tinued motion, and every one to take its fhare of 
fpace or room in the fame, according to the bulk of 
its body, or according to the particular power 
it hath to receive, and continue this or that peculiar 
motion. 

Two or more of thefe particles joyned immediately 
together, and coalefcing into one become of another 
nature, and receptive of another degree of motion 
and Vibration, and make a compounded particle 
differing in nature from each of the other par- 
ticles. 

All bulky and fenfible bodies whatfoever I fuppofe 
to be made up or compofed of fuch particles which 
have their peculiar and appropriate motions which are 
kept together by the differing or diffonant Vibrations 
of the ambient bodies or fluid. 

C According 



Do} 

According to the difference of thefe Vibrative 
motions of the Incompaffing bulks. AH bodies are 
moreorlefs powerful in preferving their peculiar 
lhapes. 

All bodies neer the Earth are incompafled with 
a fluid fubtil matter by the differing Velocity of 
whofe parts all (olid bodies are kept together in the 
peculiar ihapes, they were left in when they were la ft 
fluid. And all fluid bodies whatfoever are mixed 
with this fluid, and which is not extruded from them 
till they become fblid. 

Fluid bulks differ from folids only in this, that all 
fluids coniift of two forts of particles, the one this 
common Menftruum near the Earth, which is inter- 
fperfed between the Vibrating particles appropriated 
to that bulk, and fo participating of the motions and 
Vibrations thereof :^And the other, by excluding 
wholly, or not participating of that motion. 

Though the particles of folid bodies do by their 
Vibrative motions exclude this fluid from coming be- 
tween them where their motions do immediately 
touch, yet are there certain fpaces between them 
which are not defended by the motion of the par- 
ticles from being pervaded by* the Heterogeneous 
fluid menflruum. 

Thefe fpaces fo undefended by the bodies and Vi- 
brative motion of the particles, and confequently 
pervaded by the fubtil incompaffing Heterogeneous 
fluid are thofe we call the infenfible pores of 
bodies. 

According to the bignefsof the bodies the motions 
are, but in reciprocal proportion : That is, the big- 
ger or more powerful the body is, the flower is its 
motion with which it compounds the particles 5 and 
khe lefs the body is, the (wifter is its motion. 

The fmaller the particles of bodies are, the nearer 
do they approach to, the nature of the general fluid, 

and 



C»3 

andthemoreeaElydothey mix and participate of its 
motion. 

The Particles of all folid bodies do immediately 
touch each other, that is, .the Vibrative motions of 
the bodies do every one touch each other at every 
Vibration. For explication, Let ABC reprefent 
three bodies, each of 

thefe bodies I &p- j) A E B F G Cr 
poie to have a Vi- 



brative motion on ei- 
ther fide of it, A be- 
tween D and E,B be- 
tween E and F, and C between Fand G. I fuppofe 
then that B in every one of its Vibrations doth meet 
A at E, and C at F, and fo the motions are continually 
interchanged : That is, B communicates its motion to 
A atE,and A at thefime time and place communicates 
its motion to B, which returning to F meets there 
with C, and communicates its received motion to C, 
which at the fame inftant and place communicates its 
own motion to B, which returns it back to E : So 
that the Velocity of thefe bodies is always the fame, 
and each body imprefleth on the contiguous bodies 
fuch a determinate number of pulfes within a certain 
fpace of time. Suppofe for inftance, in every fecond 
of time B communicates to A and to C one million 
of pulles, and hath received as many from each 
of them, by which means each of them doth pre- 
ferve its own fpace of Vibration, according to the 
power of its Vibration, that neither of the contigu- 
ous bodies can enter into it. The extreme particles 
A and C are repercufled by the motion of the am- 
bient Heterogeneous fluid, whereof though the bo- 
dies are of differing magnitudes, yet the body and 
motion of the one are equivalent to the body and 
motion of the other, fo that whatever the body be 
lefs, the motion is quicker 5 and where the body is 
bigger, the motion is lefs. But the Particles of fluid 

C 2 bodies 



1**1 

bodies do not immediately touch each other, but 
permit the mixture of the other Heterogeneous fluid 
near the Earth, which ferves to communicate the mo- 
tion from particle to particle without the immediate 
contact of the Vibrations of the Particles. 

All (olid Bodies retain their folidity till by other 
extraordinary motions their natural or proper moti- 
ons become intermixed with other differing motions, 
and fo they become a bulk of compounded motions, 
which weaken each others Vibrative motions. ~o 
that though the fimilar parts do participate of each 
others motions, whereby they indeavour to joyn or 
keep together, yetdothey alio participate of an He- 
terogeneous motion which endeavours to fe pa rate 
or keep them afunder. And according to the preva- 
lency of the one or the other is the body more or lefs 
fluid or folid. 

All bodies whatsoever would be fluid were it not 
for the external Heterogeneous motion of the Am- 
bient. 

And all fluid bodies whatfoever would be un- 
bounded, and have their parts fly from each other 
were it not for (bme prevailing Heterogeneous mo- 
tion from without them that drives them more power- 
fully together,,, 

Heterogeneous motions from without are propa- 
gated within the iblid in a direct line if they hit per- 
pendicular to the fuperficies or bounds, but if ob- 
liquely in ways not direct, but different and deflected, 
according to the particular inclination of the body 
ftriking, and according to the proportion of the Par- 
ticles linking and being ft ruck. 

All fpringy bodies whatfoever conHft of parts thus 
qualified, that is, of fmall bodies indued with ap- 
propriate and peculiar motion?, whence everyone of 
thefe pai tides hath a particular Bulk, Extenhon, or 
Sphere of activity which it defends from the ingrefs 
o§ ,a,ny other incompaffing Heterogeneous body whilfl: 

in 



in its natural eftate and balance in thellniverfe. Which 
particles being all of the fame nature, that is, of 
equal bodies, and equal motions, they readily co- 
alefce and jovn together, and make up one (olid bo- 
dy, not perfectly every where contiguous, and whol- 
ly excluding the above mentioned ambient fluid, but 
permitting it in many places to pervade the fame in a 
regular order, yet not fomuch but that they do whol- 
ly exclude the fame from paffing between all the fides 
of the compounding particles. 

The parts of all fpringy bodies would, recede and 
fly from each other were tfief not kept together by 
the Heterogeneous co npreffing motions of the am- 
bient whether fluid or folid. 

Thefe principles thus hinted,. I (hall iij, the next 
place come to the particular explication ofthe man- 
ner how they ferve to explain the Phenomena of 
fpringing bodies whether folid or fluid. 

Firft for folid bodies, as Steel, Glafs, Wood, &c. 
which have a Spring both inwards and outwards, /ac- 
cording as they are either co(mpreffed, or ;dilared be- 
yond their natural iftate. 

Aia 5 WW <? 7 8.B 

[:x:i:::i;::i;zi:;:i:::!:::i 

E F 



I" r I I I I I r i 

C D 

Let A ti reprefenta line of fuch a body compound- 
ed of eight Vibrating particles, as i, ?, 3,4, 5-, 6, 7, 8, 
and fuppofe each of thofe Particles to perform a mil- 
lion of (ingle Vibrations, and confequently of oc- 
curfions with each other in a fecond minute of time, 

C $ . their * 



E 

their Motion bang of fuch a Velocity impreffed from 
the Ambient on the two extreme Particles i and g. 
Firft, if by any external power on the two extremes 
i and 8, they be removed further afunder, as to C D, 
then (hall all the Vibrative Particles be proportiona- 
bly extended, and the dumber of Vibrations, and con- 
fequentiy of occurfions be reciprocally diminiftied, 
and confequentiy their endeavour of receding rrom 
each other be reciprocally diminiftied ahb. Forfup- 
pofing this fecond DimenOon of Length be to the 
firft as 3 to 2, the length of the Vibrations, and con- 
fequentiy of occurfions, be reciprocally diminiftied. 
For whereas I fuppofed ioooooo/m a fecond of the 
former, here can (>e but 666666 in this, a»nd confe- 
quentiy the Spring inward muft be in proportion to 
the Extenfion beyond its natural 1 r-gth. 

Secondly, if by any external force the extreme par- 
ticles be removed a third part nearer together than 
C the external natural force being aiway che fame 
both in this and the former inftance, which is the bal- 
lance to it in its natural ftate ) the length of the Vi- 
brations fhall be proportionabiy diminiftied, and the 
number of them, and confequentiy of the occurfions 
be reciprocally augmented, and inftead ofioooooo, 
there (hall be 1500000. 



Having 



Having thus explained the moft fimpJe way of 
fpringing in fol id bodies, it will be yeryeafie to ex- 
plain the compound way of fpringing, that is, by 
flexure, fuppofing only two of thefe lines joyned 



H 



K 





together as at G H IK, which being fay any external 
power bended into the form L N N O, LM will be 
extended, and N O will be diminifhed in proportion 
to the flexure, and confequently thefame proportions 
and Rules for its endeavour of reftoring it feif will : 
hold. • 

In the next place for fluid bodies, amongft which 
the greateft inftance we have is although the fame be i 
in fome proportion in all other fluid bodies. 

The Air then is a body confiifing of particles f© » 
frrmll as' to be aim oft equal to the particles of the 
Heterogeneous fluid mtdium incompaffing the earth. . 
It is bounded but on one fide, namely, towards the 
earth, and is indefinitely extended upward oeing 
only hindred from flying away that way by its owe 
gravity, ( the eaute of which I (hall fome other time 
explain.) It con fifts of thefame particles fingle and 
feparated, of which water and other fluids do, con- 
foyned and compounded, and being made of particles 

exceeding ; 



exceeding final!, its motion( to make its ballance with 
the reft of the earthy bodiesjis exceeding fwift, and 
its Vibrative Spaces exceeding large, comparative to 
-the Vibrative Spaces of other terreftrial bodies. I 
fuppofe that of the Air next the Earth in its natural 
ftate may be 8000 times greater than that of Steel, 
andabove a thoufand times greater than that, of com- 
mon water, and proportionally? I luppofe that its-mo- 
tion muftbe eight thoufand times fwifter than the for- 
mer, and above a thoufand times fwifter than the la- 
ter. ' If therefore a quantity of this body be inclofed 
by'afolid body, and that be fo contrived as to com- 
prefs it into lefs room, the motion thereof ( fuppofing 
the heat the fame) will continue the fame, and con- 
fequently the Vibrations and Occurfions will be in- 
creafed in reciprocal proportion, that is, if it be 
Condenfed into half the fpace the Vibrations and 
Occurfions will be double in number : If into a quar- 
ter the Vibrations and Occurfions will be qua- 
druple, &C. '/111'. r • 1 

A^ain, If the conteining Veffel be fo contrived as 
to leave it more fpace, the length of the Vibrations 
will be proportionably inlarged, and the number of 
Vibrations and Occurfions wiUbereciprocalty dimi- 
nifhed, that is, if it be furfered to extend to twice its 
former dimenfions, its Vibrations will be twice as 
long, and the number of its Vibrations and Occurfi- 
ons will be fewer by half, and confequently itsindea- 
vours outward will be alfo weaker by half 

Thefe Explanations will ferve mutatis mutandis for 
explaining the Spring of any other Body whatfo- 

ever. 

It now remains, that I (hew how the conftitutions 
of fpringy bodies being fuch, the Vibrations of a 
Spring, or a Body moved by a Spring, equally and 
uniformly (hall be of equal duration whether they be 
greater or lefs. 

I have 



D7] 

I have here already fhewed then that the power of 
all Springs is proportionate to the degree of flexure, 
<ui%> one degree of flexure, or one fpace bended hath 
one power, two hath two, and three hath three, and 
£b forward. And every point of the fpace of flexure 
hath a peculiar power, and confequently there being 
infinite points of the fpace, there rauft be infinite de- 
grees of power. 

And confequently all thofe powers beginning from 
nought, and ending at the laft degree of tenfion or 
bending, added together into one (urn, or aggregate, 
will be in duplicate proportion to the fpace bended or 
degree of flexure 3 that is, the aggregate of the 
powers of the Spring tended from its quiefcent po- 
fture by all the intermediate points to one fpace 
f be it what length you pleafe ) is equal, or in the 
fame proportion to the fquare of one ( fuppofing 
the faid fpace infinitely divifible into the fradions of 
one 5) to two, is equal, or in the fame proportion to 
the fquare of two, that is four 5 to three is equal or 
in the fame proportion to the fquare of three, that is 
nine, and fo forward - and confequently the aggre- 
gate of the firft fpace will be one,of the fecond fpace 
will be three, of the third (pace will be five, of the 
fourth will be (even, and (b onwards in an Arithme- 
tical proportion, being the degrees or excefles by 
which thefe aggregates exceed one another. 

The Spring therefore in returning from any degree 
of flexure, to which it hath been bent by any power 
receiveth at every point of the (pace returned an 
impuife equal to the power of the Spring in that 
point of Tenfion, and in returning the whole it re- 
ceiveth the whole aggregate of all the forces belong- 
ing to the greatefl degree of that Tenfion from which 
it returned , (b a Spring bent two fpaces in its return 
receiveth four degrees of impuife, that is, three in 
the iirft fpace returning, and one in the fecond $ f® 
bent three fpaces it receiveth in its whole return nine 

D degrees 



degrees of impulfe, that is, five in the firft fpace re- 
ttaed,three in the fecond, and one in the third. 

So bent ten .{paces it receives in its whole return 
one hundred degrees of impulfe, to wit, nineteen in 
the firft, feventeen in the fecond, fifteen in the third, 
thirteen in the fourth, eleven in the fifth, nine in the 
fixth, fevenin the feventh, five in the eighth, three 
in the ninth, and onein the tenth. 

Now the comparative Velocities of any body mo- 
ved, are in fubduplicate proportion to .the aggregates 
or fums of the powers by which it is moved, therefore 
the Velocities of the whole fpaces returned are always 
in the fame proportions with thofe fpaces, they being 
both fubduplicate to the powers, and confequently 
all the times (hall be equal. 

Next for the Velocities of the parts of the fpace 
returned they will be always proportionate to the 
roots of the aggregates of the powers impreffed 
ia every of thefe fpaces 5 for in the lad: inftance 3 
where the Spring is fuppofed bent ten fpaces, 
the Velocity at the end of the firft fpace returned 
fhallbe as the root of 19. at the end of the fecond 
as the Root of 56. that is,, of 19 + 17. at the end of 
the third as the Root of 51. that is of 19 + 17 
+ 1 5. At the end of the fourth as the Root 
of 64. that is of 19 + 17 + 15 + 13. at the end of 
the tenth, or whole as th e Root of 100. that is as 

^TsT-F Tt^H 15 FF 13 + 11 +9+ 7 + 5 + 3 

+ 1, equal to 100. 

Now fince the Velocity is in the fame proportion 
to the root of the fpace, as the root of the (pace is to 
the time, it is eafie to determine the particular time 
in which every one of thefe fpaces are paffed for 
dividing the fpaces by the Velocities correfponding 
the quotients give the particular times. 

To explain this more intelligiblyjet A in the fourth 
figure reprefent the end of a Spring not bent,or at leaft 

coun- 



counterpoifedin that pofture by a power fixt to it,and 
movable with it,draw the line A B C,and let it repre- 
fent v the way in which the end of the Spring by addi- 
tional powers is to be moved, draw to the end of it 
€ at right Angles the Line C £ D d, and let C D re- 
prefent the power that is fufficient to bend or move 
the end of the Spring A to C 5 then draw the Line D A, 
and from any point of the Line A C as B B.Dra w Lines 
parallel to CD, cutting the Line D A inE,E, the 
Lines B E, B E, will reprefent the refpecYive powers 
requifite to bend the end of the Spring A to B, which 
Lines B E,B E,C D will be in the fame proportion with 
the length of the bent of the Spring A B, A B, A C. 

And becaufe the Spring hath in every point of the 
Line of bending A Qa particular power,therefore ima- 
gining infinite Lines drawn from every point of A C 
parallel to C D till they touch the Line A D, they will 
all of them fill and compoie the Triangle A CD. The 
Triangle therefore A C D will reprefent the aggregate 
of the powers of the Spring bent from A to C, and 
the lefler Triangles ABE, ABE will reprefent the 
aggregate of all the powers of the Spring bent from 
A to B, B, and the Spring bent to any point of the 
Line A C, and let go from thence will exert in its re- 
turn to A all thofe powers which are equal to the re- 
fpedtive ordinates BE, BE, in the Triangles, the fum 
of all which make up the Triangles ABE, ABE. 
And the aggregate of the powers with which it re- 
turns from any point, as from C to any point of the 
fpace CA as to BB, is equal to the Trapezium 
CDEB, CDEB, or the exceflfes of the greater 
Triangles above the lefs. 

Having therefore fhewn an Image to reprefent the 
flexure and the powers, fo as plainly to folve and an- 
fwer a41 Queftions and Problems concerning them, in 
the next place I come to reprefent the Velocities ap- 
propriated to the feveral powers. The Velocities 
then being always in a fubduplicate proportion of 

D 2 the 



i>o] 

the powers, that is, as the Root of the powers im- 
prefled, and the powers impreft being as the Trapezi- 
um or the excefs of the Triangle or fquare of the 
whole fpace to be paft above the fquare of the fpace 
yetunpaffed} if upon the Center A, and fpace AC, 
(C being the point from which the Spring is fuppofed 
let go J a Circle be defcribed as C G G F 5 and ordinates 
drawn from any point of C A the fpace to be paft, 
as from B,B* to the faid Circle,as B G,B G,thefe Lines 
BGjB G,will reprefent the Velocity of the Spring re- 
turning from C to B, B, &c. the faid ordinates being 
always in the fame proportion with the Roots of the 
Trapeziums C D E B, CDEB for putting AC = 
to a, and A B=b, BG will always be equal to 
-v(aa- bb, the fquare of the ordinate being always 
equal to the Re&angle of the intercepted parts of the 
Diameter. 

Having thus found the Velocities, to wit, B G, B G, 
AF, to find the times correfponding, on the Diame- 
ter AC draw a Parabola CHF whofe Vertex is C,and 
which paffeth through the point F. The Ordinates 
of this Parabola BH, B H, A F, are in the fame pro- 
portion with the Roots of <the fpaces C B, C B, CA, 
then making GB to HB as HB to IB, and through 
the points CIIF drawing the curve C II IF, the 
refpe&ive ordinates of this curve (hall reprefent the 
proportionate time that the Spring fpends in re- 
turning the fpaces C B, C B, CA. 

If the powers or ftiffnefs of the Spring be greater 
than what I before fuppofed, and therefore muft be 
exprefTed by the Triangle C d e A. then the Velocities 
will be the Ordinates in an Ellipfe as Cy yN, greater 
than the Circle, as it will alfo if the power be the 
fame, and the bulk moved by the Spring be Iefs. Then 
will the S-like Line of times meet with the Ltne AF 
at a point as X within the point F.But if the powers of 
ikQ Spring be weaker than I fuppofed,then will C^ee 
A.reprefent the powers, and CyyO the Ellipfis of 

Velocity.3 



[21] 

Velocity, whofe Ordinates B y, B y t A O will give the 
particular Velocities, and the S-like Line of time will 
extend beyond N . The fame will happen fuppofing 
the body ( moved by the Spring J to be propor- 
tionately heavy, and the powers of the Spring the 
fame with the firft. 

And fuppofing the power of the Spring the fame 
as at firft, bended only to B 2, and from thence let go 
B 2 E A is the Triangle of its powers, the Ordinates 
of the Circle Bg L are the Lines of its Velocity, and 
the Ordinates of the S-like Line B i F are the Lines of 
time. 

Having thus fhewed you how the Velocity of a 
Spring may be computed, it will be eafie to calcu- 
late to what diftance it will beable to (hoot or throw 
any body that is moved by it. And this muft be done 
by comparing the Velocity of the afcent of a body 
thrown with the Velocity of the defcent of Gravity, 
allowance being alfo made for the ReGftanee and in> 
pediment of the medium through which it paffes. 
For inftance, fuppofe a Bow or Spring fixed at 
16 foot above a Horizontal floor, which is near 
the fpace that a heavy body from reft will defcend 
perpendicularly in a fecond of time. If a Spring de- 
liver the body in the Horizontal line with a Velocity 
that moves it 16 foot in a fecond of time, then ffiall 
it fall at 16 foot from the perpendicular point on the 
floor over which it was delivered with inch Velocity, 
and by its motion (hall defcribe in the Air or fpace 
through which it paffes,a Parabola. If the Spring be 
bentxo twice the former Tenfion, fo as to deliver the 
body with double the Velocity in a Horizontal Line, 
that is, with a Velocity that moves 32 foot in a fe- 
cond, then fhall the body touch the floor in a point 
very near at 32, foot from the aforefaid perpen- 
dicular point, and the Line of the motion of the 
body, fo (hot fhall be moved in a Parabola, or a Line 
very near it, I fay very near it* by realbn that the 

D 3 Impediment 



D»3 

Impediment ofthe medium doth hinder the exa&nefi 
of it. If it be delivered with treble, quadruple, 
quintuple, fextuple, &c. the firft Velocity it (hall 
touch the floor at almoft treble, quadruple, quintu- 
ple, fextuple, &c. the firft diftance. I (hall not need 
tofhewthereafonwhyit is moved in a Parabola, it 
having been fuffieiently demonftrated long fince by 
many others. 

If the be delivered by the Spring at the floor, but 
fhot by fome Angle upwards, knowing with what 
Velocity the fame is moved when delivered, and with 
what Inclination to the Perpendicular the fame is di- 
rected, and the true Velocity of a falling body, you 
may eafily know tlie length of theja&us or (hot, and 
the time it will fpend in paffing that length. 

This is found by comparing the time of its afcent 
with the time of the defcent of heavy bodies. The af- 
cent of any body -is eafily known by comparing its 
Velocity with the Angle of Inclination. 

Let a b then in the fifth Figure reprefent 1 6 foot, or 
the fpace defcended by a heavy body in a fecond 
minute of time. If a body be (hot from b, in the Line 
bf with a Velocity as much fwifter than that equal 
motion of 16 foot in a fecond, as this Line £f is longer 
than a b the body fhall fall at e 3 for in the fame fpace 
of time that the oblique equal motion would make 
it afcend from bd to a c will the accelerated direct 
motion downward move it from a c to b d 9 and there- 
fore at the end of the fpace of one fecond, when the 
motions do equal and balance each other, the body 
muft be in the fame Horizontal Line in which it was at 
firft, but removed afunder by the fpace be, and for 
the points it paffeth through in all the intermediate 
fpaces this method will determine it. 

Let the Parallelogram abpq then reprefent 
the whole Velocity of the afcent of a body by 
an equal motion of 16 foot in a fecond, and 
the Triangle fqr reprefent the whole Velocity 

of 



of the accelerated defending motion, p bis then the 
Velocity with which the body is (hot, and p is 'the 
point of reft where the power of Gravity begins to 
work on the body and make it defcend. Now draw- 
ing Lines parallel to aqr^ asstu^s t gives the Velo- 
city of the point t afending, and tu the Velocity of 
thefame point t defcending. 

Again, pbst fignifles thefpace afcended, and ptu 
the fpace defended, fo that fubtracTmg the defcent 
from theafent you have the height aboye the Line b d 7 
the confideration of this, and the equal progrefs for- 
wards will give the intermediate Velocities, and de- 
termine the points of the Parabola. 

Now having the Ja&us given by this Scheme or 
Scale, appropriated to the particular Velocity, where- 
with any body is moved in this or that line of Incli- 
nation, it will be ealie to find what Velocity in any 
Inclination will throw it to any length 5 for in any 
Inclination as the fquare of the Velocity thus found in 
this Scale for any inclination is to the fquare of any 
other Velocity, fo is the diftance found by this 
Scale to the diftance anfwering to the fecond Velo- 
city. 

I have not now timeto inlarge upon thisfpeculati- 
on, which would afford matter enough to fill a Vo- 
lume, by which all the difficulties about impreffed 
and received motions, and the Velocities and effefts 
refulting would be eafily refolved. 

Nor have I now time to mention the great number 
of ufes that are and may be made of Springs in Me- 
chanick contrivances, but (hall only add, that of all 
fpringy bodies there is none comparable to the Air for 
thevaftnefs of its power of extention and contracli* 
on. Upon this Principle I remember to have feeo 
long iince in Wfdham Colledge, in the Garden of the 
learned 'Dx.WHkins^ late Biihop of Chejfor, a Foun- 
tain {o contrived as by the Spring of the included 
Ajr. to throw up to a great height a large and lafting 

ftream \ 



M 

ftreamof water : Which water was firfc forced into 
the Leaden Ciftern thereof by two force Pumps 
which did alternately work, and fo condenfe the Air 
included into a fmall Room. The contrivance of 
which Engine was not unknown to the Ancients, as 
Hero in his Sfiritalia does diffidently manifeft, nor 
were they wanting in applying it to very good ufes, 
namely, for Engines for quenching fire: As Vitruvim 
( by the help of the Ingenious Monfieur Claude Per- 
vaults interpretation ) hath acquainted us in the 
Twelfth Chapter of his Tenth Book, where he en- 
deavours todefcribe Ctefibius his Engine for quench- 
ing fire. Not long fince a German here in England 
hath added a further improvement thereof by con- 
veying the conftant ftream of water through Pipes 
made of well tanned and liquored Leather, joyned 
together to any convenient length by the help of 
brazen Screws. By which the ftream of water may 
be conveyed to any convenient place through narrow 
and otherwife inacceffible pafTages. 

The ingenious Dr. Denys Pappin hath added a fur- 
ther improvement that may be made to this Ctefibian 
Engine by a new and excellent contrivance of his own 
for making of the forcing Syringe or Pump, which at 
my defire he is pleafed to communicate to the Pub- 
liqueby this following Defcription, which he fent me 
fome time fince. 



Dr. Papp'ms 



Pay: Z£, 






1*5 ] 



Dr. Pappins Letter containing a 
Defer iption of a Wind-Fount ain 7 and 
his own particular contrivance about the 
forcer of its Syringe. 

Ince the Artificial Fountain you have feen at 
Mr. Boyles (which was of my making upon his 
defire ) hath been fo pleafing to you as to make 
you defire toiee my description thereof, I cannot 
doubt but the fame will be as grateful alfo, and well 
received by the Publick, efpecially when they (hall 
therein find a remedy for one of the greateft incon- 
veniences of forcing Pumps, which are of fo great 
ufe for raifing,of water, and quenching of fires. This 
was the occafion of my fending you this prefent de- 
fcription, which would not have been thus prolix 
had it been only for your felf. 

In the Figure then A A is the Receptacle or body 
of the Fountain careful fodered in all places, B B is 
the Pump, CC the Plug or forcer, D a Pipe in the 
middle of the Plug, which is perfectly ihut and {top- 
ped when thePlateEE is forced down upon it, EE 
is the Plate with a hole in the middle, upon whiclxis 
fodered a Pipe F, which ferves for a handle to move 
the Plug up and down. 

G is a Cock at the top of the Pipe, which ferves 
to moderate the Jetto or ftream. 

H H is a Valve at the bottom of the Pump, which 
openeth outward for the paffage of the water out of 
the Pump into the Fountain or Receptacle. 

1 1 is a Crofs at the top of the Plug to hinder the 
Plate EE from being drawn or feparated too far 

E from 



from the hole D in working it to and fro* 
RKare two Pins ferving both to force down and 
keep open the Valve H H. 

LL are two Appendices fodered unto the top of 
the Pipe F F, ferving both for a handle to the Rod 
of the forcer, and alfo to keep down the forcer. 

M M are two other appendices or buttons faftned: 
at the top of the two fmall pillars N N, fo as to turn 
upon the fame, and ferve to hafp or button down the 
ends LL of the handle of the forcer that it be not 
driven up again. 

OO is the Bafin for receiving the water that falls 
from the Jet or ftream from which it may be forced 
againinto the Fountain or Receptacle. 

For charging this Machine the Bafin O O muft firfl: 
be filled with water, and then the Pump muft be 
worked to and fro. In doing of which, when the 
Plugis drawn upwards the water in the Bafin runs in 
through the crofs ( through which the Rod F F paf- 
fes 5 ) where /finding the holeDopenit fills the fpaces 
of the bottom of the Pump 5 then the Pump being 
thus filled,, the Plug is to be forced downwards, 
whereby the Plate E E being clofely applied to the 
brims of the hole D hinders the water from return- 
ing back again through the fame, but is forced 
through the valve H H into the Fountain A A. And 
By repeating this operation all the water of the Bafin 
OOis eafily forced -into "the aforefaid Fountain, 
whereby all the Air that was therein contained is com- 
prefled more or lefs according as more or lefs water is , 
forced in, and kept in that compreflion by the valve 
H H, which hinders the water that it cannot re- 
turn through the fame. 

But when you defire to have it return, you force 
. down the Plug hard againfr, the bottom or plate, 
which by the help of the aforefaid Pins or Appen- 
dices K K force, and keep open the valve HH, and 
" F being kept faft down in this pofture by the , 

aforefaid . 



[27] 

aforefaid Buttons or Hafps M M, upon opening the 
Cock G the water returneth through the valve HH, 
fo kept open, through the hole D, and through the 
whole length of the Pipe F. 

This way of putting a valve into the Plug of for- 
cing Pumps will be of great ufe for all fuch as ferve 
for fupplying Towns with water, and for quenching 
of fire, as preventing a great inconvenience to vvhich 
the common Pumps are "ufually fubjeft from the Air 
which is apt to be generated within them, which Air 
upon working the. faid Pump remaining below the 
forcer, and by its ExpanGon when the Plug is drawn 
upwards, hindring the water from filling the whole 
Cavity beneath it, and by its Condenfation when the 
Plug is forced downwards, lofing a great part of the 
ftrength of the force, much of the effect of the faid 
Machine is fruftrated. 

For preventing of which Inconvenience care is to 
be taken that the water in all thefe forcing Pumps be 
admitted by the top thereof as in the prefent Machine, 
whereby whatever Air fhall be generated below the 
Plug, will readily rife into the hole D as being the 
higheft place next the Plate EE, from whence when 
by the drawing up of the Plug the Plate is lifted from 
the brims of the hole D the Air will readily flip up, 
and the water as readily deicend and fill all the 
parts of the Pump below the Plug. As I have often 
experimented in this prefent Machine. 

Some Perfons may objecl: againft thefe kind of 
valves, asfuppofing the preffure of the water to be on 
the wrong fide thereof. But it is eafie to be noted 
that this ob je&ion is groundlefs, fince it is the fame 
thing whether the Plate be preiled againft the Rim 
of the valve, or the Kim of the valve againft the plate. 
In common valves the Preffure of the water forceth 
the Plate againft the Rim : But in this the Rim againft 
the Plate 5 for the remaining fblid Rim of the valve, 
being; made thrice as big as the hole or Cavity thereof, 

E 2 the 



the preffure of the water againft that Rim forcetft 
the faid Rim againft the Plate in the middle three 
times harder than if the preflure of the water lay 
only on the plate of the value, the fame would be pref- 
fed againft the Rim. 



To this Difcourfe of an Artificial Fountain I 
thought it not improper to add an ingenious Dif- 
courfe of M. James Toung of Plimouih conteining his 
own Obfervations and Opinion concerning natural 
Fountains and Springs. 




Aving now gained time, from my other avo- 
cations, I have drawn up thofe obfervations. 
I 'told you I had made in my travels, which had 
confirmed in me the opinion of my Lord Bacon, that 
Fountains and Springs were the Percolation of 
the Sea 5 not ( as your fell, Mr. Ray, &c. do affert ) 
from the rains defcent into the Earth, I now repre- 
fent them to your confideration, rather as an Apology 
( becaufe they feem rational ) to excufe, than Argu- 
ments to juftifie and avow the prefumption of my 
difTent. 

The firft (hall be the Phenomena, I obferved at 
Ifle de, Mayo, which lieth in the Torrid Zone, about 
thirteen degrees and 30 minutes, North from the 
Equator. It's about fix Leagues long, and four 
broad, the wind bloweth conftantly North Eaft, or 
thereabout, and without rain, except three weeks in 
July, when it hath many fhowers } There fend you a 
Map of the liland, as exa&Jy as I could draw it. I 
was there two Voyage^ and each remained a full 
month, the bed: part of which I fpent in hunting, and 
ranging the liland 5 there runneth through the middle 
of it a 'Rivulet, of very pure, water 3 It takes its rife 

from 



file of MAYO 






Pag: zq. 



£#M! 



1 Wf 




'J)iver.s Uttle^ 



<% 



#/< 



yprwas 



-,,,# 






^4JmalL TSUhw' where 
y natives inhabit 



■JBL 






,*^>' 



./£s aper-aiis SSWfromyou j 
about 6~ Leagues Jiff; ant. 



[*93 

from the bottom of two Hills, which lie on the North 
Eaftend, The ftream at the place marked D, is about 
fourteen foot wide and two deep $ other than which 
there is no frefh water on the whole Ifland, except 
what our people dig out of the fand between the 
Ocean and the fait Pond. 

The laid Pond is in a large Bay, at the Weft fide 
of the Ifland, which hath from one point to another 
a bank of Sand, about two or three foot above water, 
covering the Bay like a firing to a Bow, the faid bank 
in the Flemiih Road is about 1 50 foot wide, at the 
Englifti Road it is as broad again :, there is never any 
fenfible ebbing or flowing of the Sea, only at foil 
Moons, or a day before. It rifeth in high Billows, 
which break over the Bank, at the North end of the 
Pond, where it is lo weft : By which means the Pond 
is replenifhed with water, which condenfeth into 
Salt in two days. 

The Sand dividing the faid Pond and the Sea is 
very fine and loofe. Now becaufe the before-men- 
tioned Rivulet difembogues far from the Roads at an 
inconvenient place for Boats, they are conftrained to 
dig Wells, in the midft of the bank of Sand, be- 
tween the Pickle^ of the fait Pond and the Sea, 
the manner thus: They firft dig a pit about eight 
foot deep, and therein lay two Hoglheads, the 
one on the top of the other, the head out of both (ave 
the lowermoft of the deepeft} the fides of both 
are alfo full of Gimlet holes, and the fand laid 
clofe to them: After twenty four hours they have 
three or four foot of very clean water in them, which 
being dipped out, you plainly fee the new water 
(train gently through thofe holes in the fides of the 
Cask : After which, in a days time, one man attend- 
ing^, may draw about tenHogiheads or more of wa- 
ter, a little tafting of Salt, not fo much but that it is 
drinkahle, and very fit to boyl meat in, and is nfed 
by thofe that come there to load Cattle^ for their^ 

E 3 common 



[303 
common drink, I have in the Map placed the Sign 
O where our Well was made. 

The next ohfervations, pertinent to this fubjeft I 
made at the Ifland Lipari, near SuUy, about fixteen 
Leagues from Mejjina '3 it is famous for thebeft Rai- 
fins in the Mediterranean ? there is on it a large Ca- 
ftle, a fmaliTown, many Vineyards, and about one 
hundred Families, befides fome Religiofe I judge it 
wants a fifth part of thebignets of the Ittede Mayo, 
it is moftly very high Land, efpecially one Mountain, 
on which (lands a Watch Tower, whence a man may 
fee amonftrousdiftanceatSea, as is confirmed by de 
Ruyter. In the relation he gives the States of Holland, 
wherein he tells them, that from that place they dif- 
cerned the French Fleet's approach long before they 
could from any other part, either of their own or 
the other Ifland. I am fure it is much higher than 
either that at the Ifle de Mayo, or any I have feen in 
England, and yet on this fair fruitful Ifland fprings 
not one drop of water, the Inhabitants ftoring them- 
felves with rain, which falling very frequently, they 
are careful, to preferve in Cifterns, divers efTays have 
been made in the moft promifing part of it to find 
Springs by digging Wells, one ofthofe which I faw 
was without doubt the deepen: in Europe, I remem- 
ber not the exad: profundity as they related it, but I 
have not forgot, that throwing in a ftone it was 
long ere it got to the bottom, and then returned 
fuch a noife as it had been the difcharge of a 
Mufquet. 

The caufe of this drinefs was by the people 
thought to be fubterranean heats, abfuming the water, 
but no fuch thing appearing, to the fenfe of thofe 
that digged the Wells, I gave no faith to that per- 
fuafion 3 they fancy fuch heats partly from the want 
of water, but moftly becaufe the four adjacent 
Iflands, Stromboli, Vulcano, VnlcaneUa, and M, JEtna, 
are conftantly burning, and very near them. 

The 



The obvious earth of this place is loofe, and in all 
apparent qualities very good, but by the heaps that 
had been thrown up, in digging the Wells, I faw the 
inferiour earth was clammy, or like clay, that had 
fome greafie gummous matter commixed, This the 
Religious told me was the very kind of Sulphur 
which conftantly boy led out of the burning Cranny 
onVulcanella^ and wherewith all thofe fflands abound- 
ed, not excepting their own, though it were not yet 
kindled. 

For my third obfervation, I will go no farther than 
the place of my prefent abode, Plimmonth^ in which 
on a kind of Piazza, commonly called the New-key^ 
( a plat of ground got in from the Sea ) is a Weil, 
which ( before the ever famous Sir Francis Drake by 
cutting a Rivulet of thirty miles procured us water 
in great plenty ) was of common ufe, having ( as at 
this day ) a Pump in it 3 about feven years fince ( be- 
ing before the Key was inlarged) the Well was not 
above eight foot from the edge thereof, over which 
the Sea would frequently flow, when a high out- 
wind and a Spring Tide concurred, I fay this Well, 
though fo near the Sea, yieldeth clean water, and as 
fweetasa mixture of three parts frelh and one of fait 
water would be. About an hundred yards from that 3 
on ground a little riling, is a very large Well, which 
fupplieth three or four Brew-houfes, by whofe drink 
it is evident that the water hath not wholly quitted 
its fait. It is to be noted, that Plimmouth Ireth on a 
Peninfula three miles long, and two broad, the Ifth-- 
mus about two thirds of a mile wide, and not very 
high from the furface of a full Sea. There are many 
Wells in it, thofe near the Sea are faltifh, thofe far- 
ther from it the lefs fo. 

My fourth obfervation I take from the late famous 
French Traveller Mon fie u r IWmer, who in his firft .. 
Volume, . difcourfing of the Coaft of Coromandil y &rc„ . 
he faith they there want frefh water, and are con- 

ftrainedi 



drained to make^its of two foot deep in thefand by 
the Sea to find it. 

The fifth obfervation, and which I would call the 
moft fignificant, were I allured of its truth, I had 
from a very ingenious Chirurgeon, who had ufed the 
Weft Indias, that there is in that Sea an Ifland called 
Rotunda, of a figure agreeable to its name, which, 
though very fmall, hath on it, arifing in the middle, 
a Spring of a very large ftream of water, at which 
our Ships frequently furnifh themfelves in their Navi- 
gation, he affirmed that it raineth there but once a 
year, asatthelflede Mayo 3 faying withal, that the 
Ifland is foihort of a proportion big enough for the 
ftream, that if it conftantly rained, it could not be 
fupply enough to maintain fo large an Efflux. 

My fixtk and laft, is the relation of Dr. Downes 
concerning Barbadoes, viz. that all their Springs were 
formerly very near the Sea 5 that up in the Country 
they fupplied themfelves from the rains by digging 
pits in the earth, able to contain great quantities, and 
there preferving it 5 which they did a very long time 
C the rains being there as unfrequent as at the lfle de 
Mayo ) and that without any fenfible diminution by 
penetrating and defending into the earthy and to 
prevent the lofs thereof by the exhalations of the 
Sun they covered it with leaves, &c, but that now by 
digging deeper they find Springs fo plenty that no 
Plantation is without one. 

From all thefeobfervations the following confe&a- 
ries do mechanically refult. 

From the firft it appeareth that fbme Springs have 
manifeftly their fburce from the Sea 5 that fand fwee- 
tens tranfcolated Sea^water, and that even pickle 
ftrained through itlofeth much of its faltnefs thereby, 
all which is evident from the Well therein mentioned, 
whofe water could not poffibly be other than what 
foaked in from the Pond a.nd the Ocean. 

Hence 



M 

Hence alfo is manifeft, that conftant and large 
Fluxes of water may be made for eleventh months 
without rain to refill the fubterranean Cifterns, fup- 
pofed by you to fupply them f this appears from the 
River running through the Ifland, by whofe banks 
Hound (it being April when I was there, at which 
time they had been ten months without rain ) thfh 
after their fhowers it could run but little larger that 
it did after fo tedious a want of them. I had forgot 
to intimate in the relation, that thofe two Hommets, 
A. are craggy Rocks, whereon live a great number 
of Goats, and are confequently very unfit, if not 
incapable, either to receive, or contain the Magazine 
for the fupply of the Rivulet. \ 

From thefecondit ismanifeft, that higher Moun- 
tains of earth, and confequently more likely to re- 
ceive and contain fufficient quantity of rain-water to 
beget and fupply Springs and Rivers have not always 
that erTeQ", although there was one great advantage 
more added here, vi%. a clammy tyte earth in the 
bottom to make the fuppofed Ciftern the better able 
to contain the (lore. I fay, that frequent rain to fill, 
high Mountains to contain, loofe pervious earth to 
receive, and a well luted bottom to fupport and re^ 
tain (being all the qualifications and circumftances 
fuppofed neceffary to make and continue Springs ac- 
cording to the modern Hypothefis J though all here 
concurred, did notwithftanding fail of producing that 
effecl. 

From the fame it is alfo manifeft,that where Springs 
fail, without want of the caufes that Hypothefis fup- 
pofeth neceffary to produce them, the occafion hath 
been from an apparent defeft in the other (that is the 
impervioufnefs of the earth through which the water 
muftpafs before a Spring can be produced) both thefe 
appeared at Lipary, where the general effecl: a Spring 
or fountain was wanting, together with the caufes 
of our Hypothefis., though thefe of the other were 

F manifeflly 



C34l 
manifeftly exiftent, and with all the advantages ne- 
cefiary: It feeming to me a very rational conjecture, 
that the greafie clammy Sulphur* wherewith that 
earth was impregnated, did by oppilating it hinder 
the infinuation of the Sea into it. 

From the third obfervation you have the firft de~ 
duftion confirmed, viz. That Springs are fometimes 
manifeftly from the Sea 5 That earth fweetens Sea- wa- 
ter by Percolation, And that the nearer Springs are 
to the Sea, the more they retain of their priftine falt- 
nefs, and lofe it by fenfihle degrees, as they inflnuate 
farther through it. 

By the fourth the fame is confirmed. 

The, fifth proveth, that large ftreams flow without 
any poffibility of being fupplied by rain, both for 
want of fuch rain, and of dimenfions to receive and 
contain it. 

The fixth doth evidence, that rain doth not pene- 
trate the Surface of the earth, even in a very dry 
parched Country, and in the Torrid Zone, and yet 
that Springs are under it, which at once proves ours, 
and refutes the other opinion , the former appears by 
the water in thofe made Ponds, lying there for a 
long time without any fenfible lofs thereof by its leak- 
ing into the earth : The later by the Wells near the 
Sea, and thofe found fince under that impervious. 
Land. 

He that is not altogether a ftranger to the weight, 
prelTure, and Elafticity of the air, the afcenfion of 
liquors through Filters, and feme other refembling 
Phenomena, would not account the like motion of 
the tranfcolated water to high hills, to be an obje- 
ction of any force againft this Hypothefis, but fure 
fuch folutions arfc no lefs beyond my ability than 
defign. 

Finding I have Paper enough left, I will prefume 
to trouble you with one rare appearance more, that 
occurred to om Mx.Brafejt of this Town, an aged 

and 



[35] 
and very fat man, who by taking Spirit of Vitriol 
in his mornings draughts ( to which he was advifed 
as a remedy to affwage the exuberance of his belly J 
found that it had no efFe& on his body 3 but that a 
bundle of Keys, which he ufed to carry always about 
him, and that wonted to be very fmooth and bright, 
of a fudden became black and rufty, though he ne- 
ver handled the Spirit 5 nor carried it in his pocket, fo 
that we concurred in opinion that the fudorous Efflu- 
via of his body, impregnated with the Acid Spirit, had 
occasioned it. 

If fo, It's very wonderful, thatfofmall a quantity 
thereof, when diluted with fo much juice as is con- 
tained in fuch a corpulent man, fhould even in (team 
and the infenfible Emanations make impreffions on 
fmooth Iron, mauger the perpetual attrition, by car- 
rying them in his Pocket, whereby fuch an effecT: 
(one would think) (hould be prevented, or foon rub- 
bed of.— I was going to make fbme reflexions on 
this notable accident, but I confider 5 dv. - 



Plim mouth 



Phm mouth rf , cv/ 

J&M.1678. fdmes loung* 



F 2 The 



p H E Original of Springs is that which hath ex- 
ercifed the Pens, of many learned Writers, 
and very various have been- the eonje&ures concern- 
ning it. But amongft all I have met with I conceive 
none mor.e probable than that which feemsto fetch its 
original from; the Hiftory of the Creation mentioned 
in Holy Writ ^ that is, that there is a Magazine of 
waters aboveas well as a Receptacle of Waters upon 
or beneath the Surface of the Earth: And that the 
Air is that Firmament which feparates between the 
upper and lower waters, and between theie two is 
the circulation of waters for bloud of the Micro- 
cofm, if I may fo call it ) performed. The water be- 
ing fometimes by a particular conftitution of the Air 
aijiftedby heat, rarified and feparated into minuter 
parts, and fo reduced into the form of Air, and 
thereby being divided into Particles really fmaller 
than thofe of the air in compaffing, and agitated with 
a greater degree of motion, they take up more fpace, 
and fo become lighter than the Ambient, and are 
thereby elevated and protruded upwards till they 
come to their place of poife or Equilibrium in the 
Air: At other times by a differing conftitution of 
the Air and deficiency iof heat they lofe their agitati- 
on, and many of them again coalefce, and fo having 
lefs motion they condenfe and revert into water, and 
ih^ being heavier than the incompaffing Air, defcend 
dpwn again to the Earth in Mills, Rain, Snow, Hail, 
or the like. 

Thatthere is fuch a Circulation! think there is none 
dpubtSjbut ftill it remains a difficulty (with thofe.. per- 
fons that grant this) that all Rivers and Springs fhould 
have their original from the water that falls or con- 
dances out of tfhe Air. 

To perfiiadefuch perfonsit may not poffibly be un- 
fuccefsful to mention : 

Firft, 



[37] 

Firft, That the great inundations or overflowing 
of Rivers manifeftly proceed either from the Rain 
that immediately falls,or from the melting of Snow or 
Ice that hath formerly fallen on the more eminent parts 
of Mountains 3 to confirm which, Hiftories enough 
might be brought were it neceffary ofNilus,NigcrJkc 

Secondly, That it hath been obferved and compu- 
ted that communibm annk & lock 5 there falls water 
enough from the Sky in a&ual Rain,Snow, or Hail up- 
on the Surface of "England to fupply all the water that 
runs back into the Sea by the Rivers, and alfo all that 
-may befuppofed to evaporate^, nay,though the quan- 
tity of the firft be fiippofed twice a^much as really it 
is. This I have been affured by thofe that have both 
experimented and calculated it, 

Thirdly, That there is not yet certainly ("that! 
know or have heard of ) any other way of making 
fait water frefh, but by Diftillation 5 which, had there? 
been fuch an Art, it would in all probability have 
been made ufe of, and fo there is little probability that 
the Springs at the top of a high Hill (hould proceed 
from the Sea-water ftrained through the earth. But 
were there fuch a filtration known I hinted in my At- 
tempt, publifhed anno 1660 about Filtration, how 
ibmewhat of that kind might be explained. 

Fourthly, That this Operation is conftantly and 
mod certainly performed by Nature both in exhaling 
and drawing up frefti (teams and vapours from the Sea s 
and all moyft bodies, and in precipitating them down 
again in Rain, Snow, Hail, but of the other we have 
no certainty. 

Fifthly, I have obferved in feveral places where a 
Tree hath flood upon an high Hill, fingly and parti- 
cularly at the brow of Box Hill mar Dar king in Sur- 
ry, that the body of the Tree is continually wet, and 
at the root fbme quantity of water, which is always 
foaking and gliding down from the Branches and bo- 
dy of the Tree, the leaves, fprigs, and branches of 

F 2 



m 

the faid trees colle&ing and condenfing continually 
the moyft part of the Air, the fame being indeed a 
true and lively reprefentation of a River. Nor 
has it been my obfervation alone, but the fame is 
mentioned by divers Authors: And it is affirmed 
by fome Authors, that there are fome Iflands in the 
Torrid Zone which have no other water in them 
than what is condenfed out of the Air by the Trees 
" at the tops of the Hills, and converted into drops of 
Rain. 

Sixthly, That it is generally obferved, whereever 
there are high Hills there are generally many Springs 
round about the bottoms of them of very frefh and 
clear water, and often times fome which rife very 
near the tops of them, which feems to proceed from 
their great elevation above the other plain fuperficial 
parts of the earth, whereby the Air being dafhed 
and broken againft them, they help to condenfe the 
vapours that are elevated into the higher and cooler 
Regions of the Air, and fo ferve likeFiltres to draw 
down thofe vapours fo condenfed,. and convey them 
into the Valleys beneath, And hence it is very ufual 
in Countries where there are high Hills to fee the tops 
of them often covered with clouds and mifts, when 
it is clear and dry weather beneath in the Valleys. 
And in the paffing through thofe clouds on the top 
I have very often found in them very thick mifts and 
frnall rain, whereas as foon as I have defcended from 
the higher into the lower parts of the Hills, none of 
that mift or rain hath fallen there, though I could ftill 
perceive the fame mifts to remain about the top. Con- 
sonant to this Obfervation was one related tome by 
an ingenious Oentleman Mr. G.T. who out of curi- 
ofity with other Gentlemen whilft he lived in the 
Ifland ofTenerijfc one of the Canaries made a journey 
to the top of that prodigious high Mountain, called 
the Pikjc. The fubftance of which ( to this purpofe ) 
Was, that the Caldera or hollow Cavity, at the very 

top 



l39l 

top thereof he obferved to be very flabby and moyfb 
and the earth to flip underneath his feet, being a very 
moyft foft Clay or Lome like mortar. And farther^ 
that at a Cave, not far from the top, there was a 
great quantity of very frefh water, which was con- 
tinually fupplied, though great quantities of Ice were 
continually fetchcl from thence, and carried down 
into the Ifland for cooling their Wines. Confonant 
to which Obfervation was that which was related to 
me by the Inquifitive Mr. Edmund Hallj made in 
St. Helena whilft he flayed there to obferve the places 
of the Stars of the Southern Hemifphere, in order to 
perfeft the Cceleftial Globe. Having then placed 
himfelfupon one of the higheft Prominences of that 
fmall Ifland, which he found to be nolefs than 3000 
foot Perpendicularly above the Surface of the Sea 
next adjoyning, fuppofing that might be the moft 
convenient place for his defigned obfervation 5 He 
quickly found his expectation much deceived as to 
that purpofe for which he chofe it $ for being gotten 
fo high into the Air the motion of it was fo violent as 
much to difturb his Inftruments$ but which was more 5 
he found fuch abundance of mifts and moyfture that 
it unglued the Tubes, and covered his Glalfes pre- 
fently with a Dew 3 and which was yet more, the 
foggs and mifts almoft continually hindred the fight 
of the Stars. But upon removing to a lower Oration 
in the Ifland he was freed from the former Incon- 
veniences. 

I could relate many Hiftories of this nature, where- 
by it feems very probable, that not only Hills, but 
Woods alfb, do very much contribute to the con- 
dcnling of the moyfture of the Air, and converting 
it into water, and thereby to fupply the Springs and 
Rivulets with frefti water: And I am confident, who- 
foever fhall confider his own obfervation of this na- 
ture, and compare them with this Theory, will find 
many arguments to confirm it. However, Nnllius m 

verba % 



L4o] 

verba, Let Truth only prevail, and Theories fignifie 
no further than right reafpning from accurate Obfer- 
vations and Experiments doth confirm and agree with 
them. 

Having thus delivered here fomewhat of my own 
thoughts concerning Springs and Rivers, finding 
among fome of my Papers a Relation, wherein a very 
ftrange fubterraneous Ciftern is mentioned, I have 
here fubjoyned it as I received it from Mr. Thomas 
Alcock. from Brijiol who together with Sir Humphry 
Hookew&s by whilft Captain Samuel Sturmy made this 
inquiry, and who by interrogatories made to him, 
pennd this Relation for him as it follows ver- 
batim,, 

IN purfuance of His Ma jefties Commands to meat 
the prefenting of my 'Mariners Magazine, I have 
with much diligence, fome charge and peril endeavou- 
red to difcover that great Concavity in the earth mGlo- 
ceflerjhire, four miles from Kingrode, where His Ma- 
jefties great Ships ride in the Severn, And I find by 
experience that what has been reported of that place 
is fabulous, whilft I thus defcribe it. 

Upon the fecond of July 1669. I descended by 
Ropes affixt at the top of ' an old Lead Oare 
Pit, four Fathoms almoft perpendicular, and from 
thence three Fathoms more obliquely, between two 
great Rocks, where I found the mouth of thisfpaci- 
ous place, from which a Mine-man and my felf 
lowerd our felvcs by Ropes twenty five Fathoms per* 
pendicular, into a very large place indeed, reiem- 
bling to us the form of a Horfe-lhoo 5 for we ftuck 
lighted Candles all the way we went, to difcover 
what we could find remarkable 5 at length we came 
to a River or great Water, which I found to be twenty 
fathoms broad, and eight fathoms deep. The Mine- 
man would have perfwaded me, that this River 
Ebbed and Flowed, for that fome ten fathoms above 

the 



L40 
the place we now were in we found the Water had 
(" fbmetime ) been, but I proved the contrary by- 
day ing there from three hours Floud to two hours 
Ebb, in which time we found no alteration of this 
River 3 befides, it's waters were fre&, fweet, and 
cool, and the Surface of this water as it is now at 
eight fathom deep, lies lower than the bottom of any 
part of the Severn Sea near us, fo that it can have no 
community with it, and confequently neither flux nor 
reflux, but in Winter and Summer, as all Stagvas, 
Lakes, and Loughs (which I take this to be J has. 
As we were walking by this River thirty two fa- 
thoms underground, we difcovered a great hollow- 
nefs in a Rock feme thirty foot above us, fo that I got 
a Ladder down to us, and the Mine-man went up the 
Ladder to that place, and walk'd into it about three- 
fcore and ten paces, till he juft loft fight of me, and 
from thence chearfully calPd to me, and told me, he 
had found what he look'd for ( a rich Mine 5 ) but his 
joy wasprefently changed into amazement, and here- 
turned affrighted by the fight of an evil Spirit, which 
we cannot perfwadehim but he faw, and for that rea- 
fonwill go thither no more. 

Here are abundance of ftrange places, the floor- 
ing being a kind of a white ftone, Enameled with 
Lead Oare, and the Pendent Rocks were glazed 
with Salt-Peter which diftilled upon them from above, 
and time had petrified. 

After fome hours fray there, we afcended without 
much hurt, other than fcratching our felves in divers 
places by climing the {harp Rocks, but four days to- 
gether after my return from thence I was troubled 
withanunufualand violent Headach, which I impute 
to my being in that Vault. This is a true account of 
that place fo much talk't of, defcribed by me 

Samuel Sturmy* 
O Having 




Having given you a Relation of fomething very 
low within the bowels of the Earth, I now (hall add, 

An account of a 'journey made to the higheft part of the 
earthhy my Ingenious Friend Mr. G.T. as J collected 
it out of the Memorials which he writ at the time of: 
making it 5 The particulars whereof were, 

1 Hat Augufi the twentieth, 1 674.about Nine in the 
morning, in company with Dr. Sebajiian de 
Franques, Mr. Chrifiopher > Prancis, Mr, Thomas Proud- 
foot, together with a Guide, and two other men with 
hories to carry themfelves and neceffary providon for 
the Journey, he fet out from 

They palled up a Hill, which was very fteep, till 
they came to the Pinal or Wood of Pines. This 
Wood li'eth very high in thelfland, and extendeth it 
felffrom one encVof thelfland to the other, and is in 
many places of a great Breadth, and is very frequent- 
ly covered with a Bruma, fog, ormift, which is fo 
thick as to darken and hinder the appearance of the 
Sun through it, and fo moyft as to-make one wet in 
parling through it. 

Through this Wood they rode by a pretty fteep 
afcent near two Leagues, croffing it till they came to 
the further or fide, where alighting they refted 

themfelves under a Pine, and Dined. And the fog, 
which had accompanied them through the whole 
Wood, here leftthem, and the Sun appeared. 

From hence they parted about one in the After- 
noon, and after an afcent of about half a mile of very 
bad ftony way they came to a fandy way, which for 
about the length of a League wa§ pretty plain 5 but 
then they began to afcend a fandy hill, which for half, 
a League farther was pretty fteep, which having 
palled they arrived at the foot of the Pike. 

Here they alighted, and then refted themfelves 
jmetime, then taking horfe again, they began 

to 



£43] 
to afcend the Pike it felf. This part of it was Co 
fteepthat the way up it is made by feveral turnings 
and windings to and fro to eafe and alleviate the 
fteepnefs of the afcent, which were otherwife un- 
paffable for horfes. All this part feems to be nothing 
elfebut burnt ftones and afhes, which may have for- 
merly tumbled down from the higher parts of the Pike; 

At. this place they alighted, and unloaded their 
horfes of the Provifion of Vi&ual and water which 
they were forced to carry with them for their own 
accommodation, as aho of the Provender for their 
horfes. And prefently fet themfelves to provide 
againft the inconveniences of the enfuing night by 
getting together in the 'firft place a good quantity of 
the wood of a (mall fhrub, called Retamen,not much 
unlike our Englilh Broom, which grows there pretty 
plentifully, and when dry burns very well $ then, ha- 
ving gotten wood enough, they endeavoured to fhel- 
ter themfelves againft the piercing cold wind by heap- 
ing up a wall of ftones on the windward fide, and 
making a good fire of the dry (hrubs they had collect- 
ed to warm themfelves. 

But fo furious was the wind which came pouring 
down from each fide of the Mountain that it blew the 
fmoak and afhes into their eyes, and forced them 
( though much to their Regret by reafon of the ex- 
treme piercing coldnefs of the Air ) to remove their 
fire farther off. And to keep themfelves as warm as 
they could by lying down upon the ground very clofe 
together. Thus they paffed the night together as 
well as they could, but with very little deep, partly 
by reafon of the cold, and partly for the continual 
expectation they had of the moment when their Guide 
would call them to be mounting up the Pikg^ which is 
ufiially about two or three hours before day, to the 
end that they may get up to the top before the 
rifing of the Sun. For at the riling of the Sun 
the Air is the moft clear, and all the Iflands of 

G 2 



[44T 
the \Ccwartu round about may be. then plainly diCco 
vered. 

But at two a clock, when they fhould have been 
on their Journey, the wind continued to blow with 
fuch violence, that their Guide would ( by no means 
venter to go up for fear lead in the climbing up fome 
fteep places the. wind fhould encounter any of them, 
and hurl them headlong down, Co that they were 
forced to continue and flielter themielves in their bad 
Lodgings till the Sun arofe, and had got fome maftery 
©f T the/wind. 

About fix a clock therefore they fet forwards oa 
their enterprife, having firft taken each of them his 
difh of Chocolatte to fortifie their ftomachs the bet- 
ter againd the cold, (6 with their Bottle of Strong- 
water in their Pockets, and Staves in their hands, 
they began to mount the Pike, the way being juft fiich 
as they had pafled the. night before,. but much more 
fteep, and continued on till they came to the Mai 
fays, or ftony way, which may be about half a mile 
from the place where they lay 5 This ftony way lieth 
upon a very fteep afcent, and is compounded of abun- 
dance of ftones which lie hollow andloofe, fome of 
them of avaft prodigious bignefs, and others of them 
fmaller, in fuch manner as if they had been thrown 
up there by fome Earthquake, as the Author con- 
jectures with very great probability. In the clam- 
bring up thefe (tones they took great care in placing 
their ftepson fuch of them as were more firm for fear 
of flipping, or tumbling fo as to break their Legs or 
Arms.. 

With this difficulty they afcended till they came to 
the Cave which he conjectures to be about three quar^ 
ters of a mile diftant from the beginning of the ftony 
way. - 

At this Cave they found feveral perfons who were 
come thither to get out Ice to carry down into the 
Ifland, fome of which were below in the Cave* 

digging 



[45] \ h* 

digging Ice which was very thick, others remained 
above. They found the mouth of the Cave about 
three yards high, and two yards broad 5 and being all 
of them defiroustodefcendintoit, by a Rope faftned 
about their bodies under their armpits they were all 
one after another let down into it till they came to 
fet their feet upon the Ice, which is about fixteen or 
eighteen foot from the mouth. 

The Cave is not very large, but full of water and 
Ice, which at the time when they were there lay 
about a foot under the Surface of the water, though 
the men that ufually go thither faid that at other 
times they found the Ice above the water ? which 
makes many to fappofe that it; ebbs and flows by means* 
of fome fecret entercourfe that it may have with the 
Sea, they averring that they have feen it emptying of 
it (elf. 

But this Gentleman fo foon as ever he came down 
fixt his eye upon a ftone that lay juft above the Su- 
perficies of the water, and obferved very diligently 
but could not in all thefpace thaTheftaid there, which 
was half an hour, find it either increase or diminifh, 
which makes-him believe that the fulnelsor emptinefs 
of the water may rather proceed from thofe thick- 
fogs and milts which are generally on the top; and 
which hinder the Pike from being feen fometimes for 
twenty, thirty, nay, forty days together, except only 
juft at the rifing or fetting of the Sun, though at fome 
other times it happens alio that the Air is clearer, and 
the Pik§ may be feen perhaps for a month together.' . 
From thefe mifts he conceives at fome times much 
water may be colle&ed at the upper parts of the Pikg y 
and (baking down may not only fupply, but increafe 
the water in the Cave 5 and confonant to this Hypo- 
thesis he obferved v/hilft he was there, that there was* 
a continual gleeting and dropping of water in fix or 
feven places from the fides of the Cave, which drop- 1 
pings he fuppofes may be greater or lefs according as- 

G 3 , thofe 



[4<n 

thofe fogs do more or lefs encompafs it, or ftay about 
it a longer or fliorter time 5 He judges alfo that there 
may be fbme other more fecret ways both for the 
conveying water into and out of the faid Cave than 
thofe droppings, but fuppofes them to proceed from 
the aforefaid fogs. Hence he concludes when the 
Air is clear, and none of thofe fogs condenfed about 
the Hill, the water in the Cave muft neceffarily de- 
creafe. And that wich confirmed him the more in 
this opinion was that when he came to the very top 
of the Pik§* he found the earth under him fo very 
moyft, that it was like mud or morter, and might be 
made into Pafte as by experiment he found which he 
conjectures could no ways be caufed by the wind or 
clear Air, which is rather drying and confuming of 
moifture, but muft proceed from the fogs or mifts 
which are above the very top of the Pike. 

He further took notice in the Cave that upon the 
fides and top thereof there grew a fhow-white furring 
like Saltpeter, which had a kind of Faltifntafte, fome 
of which he gathered and brought back with him to 
England to have it examined. 

After about half an hours ftay in the Cave, which 
they found warmer than without in the open Air, 
they were all pulled up again, and proceeded forward 
in their Journey by continuing to clamber up the ftony 
way, which lafted till they came to the foot of that 
part of the Mountain which is called the Sugar-loaf, 
by reafon that at a diftance from the Ifland it appears 
of that (hape, as it doth alfb even when you are at it. 
The diftance of this place from the Cave they judged 
to be about half a mile, but the way much more 
fteepand afcending than the former part of the ftony 
way, and extreme troublefom to pafs, their feet fink- 
ing and flipping down again almoft as much as they 
could ftnde upwards, fb that they concluded it the 
moft painful' of all $ however, perfifting in their en- 
deavours, after many times refting themfelves, they 

gained 



[47] 
gained the top 9 which they conceive might be about 
half a mile higher. 

The very top they found not plain, but very 
Rocky and uneven, and in the middle thereof a deep 
hole 5 the outfide of this top this Gentleman con- 
ceived might be about a quarter of a mile round about 
on the outfide. 

This hole he conceived to be the mouth of a VnU 
cano which hath formerly been in that place, for 
even at that time whilft they were there much 
fmoak afcended out of feveral holes and chinks of 
the Rocks, and the earth in divers parts was ftill fo 
very hot as to be very ofTenfive to their feet through 
their fhooes, and he obferved Brimftone thrown up 
in feveral places, of which he collected fbme, and 
brought back with him to England. 

From this place may be feen in a clear day all the 
fix adjacent Iflands, but the weather being then fome- 
what thick and hazy, they could difcover none but 
the grand Canaries, Palm, and the Gowera, which 
laft, though diftant near eight Leagues from the bot- 
tom of the Pike feemed yet fo near unto them as if it 
had been almoft under them. The reft of the Iflands . 
they could difcover whereabout they lay by means of. 
a kind of white cloud hanging on them, . but they 
could not difcern the Iflands through "thofe clouds. 

Here they tried their Cordial Waters which they 
carried in their Pockets, but found them not to abate 
of their ufual ftrength, and become cold and infipid 
as fair water, as feveral had pofitively averred to him 
that they had found it, but he conceived them to be 
very much of the fame nature and ftrength that they 
were of before they were carried up, which he fup- 
pofesto bebyreafon of their arriving at the top fo * 
late. 

After they had flayed on the top-about-- an hour, 
and fatisfied themfelves in obferving fuctr things a<r> 
they were able, they defcended again with very much 

facility. 



148 ] 

facility, and came to the Stancia about eleven of the 
clock, where they dined, and thence about one in the 
Afternoon let forwards for the Villa, where they ar- 
rived that afternoon about five that Evening. 

After their return they found their faces (by rea- 
fon of the heat of the Sun, and the parching fubtil 
wind ) to call: their skins. 

He did not meafure the Perpendicular height of the 
Hill hirnfelf, but fays that he hath been informed by 
divers skilful Seamen, ( who by their bed obfervation 
have taken the height -of it) that it is between three 
and four miles perpendicularly above the Sea. 

IN this Relation His very remarkable : 
Firft, that this prodigious high Hill is the Product 
of an Earthquake, and feems heretofore to have been 
zVulcana, or burning Mountain, like thofe of JEtna, 
Vesuvius, Hecla, &c. though at prefent it hath only 
fire enough left to fend forth fome few fulphureous 
fumes, and to make the earth of the Caldera or hol- 
low pit at the very top thereof in feme places almoft 
hot enough to burn their fhooes that pafs over it. And 
poffibly in fucceeding Ages even this little fire may be 
quite extinct, and then no other fign thereof may be 
left but a prodigioufly high Rock or fpiring Moun- 
tain, which in trad of time may by degrees wafte and 
be diminifhed into a Hill of a more moderate height. ,; 
Now as this Hill feems very evidently to be the 
effect of an Earthquake, fo I am apt to believe that 
mod, if not all, other Hills of the world whatever 
may have been the fame way generated. Nay, not 
only all the Hills, but alfo the Land which appears 
above the face of the waters. And for this I could 
produce very many Hiftories and Arguments that 
Would make it feem very probable, but thatlreferve 
them in the Lectures which I read of this fubject in 
Qrejham Colledge in the years 1664, and 1665-, 
which when I can have time to perufe I may publifh. 

Therein 



Therein I made it probable that moft Iflandshave 
been thrown up by fbme fubterraneous Eruptions, 
Such is the Ifland of Afcenfton, the Moluccas^ 8c c. 

Secondly that moil part of the Surface of the 
Earth hath been fince the Creation changed in its po- 
fition and height in refped of the Sea, to wit, many 
parts which are now dry Land, and lie above the Sq^^ 
have been in former Ages covered with it 3 and 
that many parts, which are now covered with the Sea, 
were in former times dry Land. Mountains have 
been funk into Plains, and Plains have been raifed 
into Mountains. , 

Of thefe by obfervations I have given inftances, 
and (hewed that divers parts of England, have in for- 
mer times been covered with the Sea*, there being 
found at this day in the moft Inland parts thereof dif- 
fident evidences to prove it, to wit, Shells of divers 
forts of Fifhes, many of which yet remain of the ani- 
mal fubftance, though others be found petrified and 
converted into ftone. Some of thefe are found raifed 
to the tops of the higheft Mountains, others funk in- 
to the bottoms of thedeepeft Mines and Wells, nay, 
in the very bowels of the Mountains and Quarries of 
Stone. I have added alfo divers other inftances to 
prove the fame thing of other parts of Europe, and 
have manifefted, not only that the lower and plainer 
parts thereof have been under the Sea, but that even 
the higheft Alpine and Pyrenean Mountains have run 
the fame fate. Many Inftances of the like nature I have 
alfo met with in Relations and obfervations made in 
the Ea(i as well as in the Weft Indies, 

Of all which ftrange occurrences I can conceive no 
caufe more probable than Earthquakes and fubterra- 
neous Eruptions which Hiftories do fufficiently. afFure 
us have changed Sea into Land, and Land into Sea, 
Vales into Mountains fometimes, into Lakes and 
AbyfTesat other times 3 and the contrary — ■ unlefs we 
may be allowed to. fuppofe that the water or fluid 

H pari: 



part of the earth which covered the whole atfiri\ 
and afterward the greateft part thereof, might in ma- 
ny Ages and long procefs of time be wafted, by being, 
firftraifed into the Atmofphere in vapours, and thence 
by the diurnal, but principally by the annual motion 
thereof be loft into the atkr, or medium through 
which itpafles, fomewhat like that wafting which I 
have obferved to be in Comets, and have noted it in 
my Coweta: Or unlefswemay be allowed to fuppofe 
that this fluid part is wafted by the petrifa&ion and 
fixation of fuch parts of it as have fallen on the Land 
and Hills, and never returned to fill up the meafare of 
the Sea, out of which it was exhaled, for which ve- 
ry much may be faid to make it probable that the 
water of the earth is this way daily diminiftied. 

Or unlefs(finceweareafcertained by obfervations 
that the dire&ion of the Axis of the earth is changed, 
and grown nearer the Polar Star than formerly 5 that 
the Magnetifm or Magnetieal Poles are varied, and do 
daily move from the places where they lately were, 
and that there are. other great and noted changes ef- 
fected in the earth) we may be allowed to conceive 
that the Central point of the attractive or gravitating 
power of the earth hath in long procefs of time been 
changed and removed alfo farther from us towards 
our Antipodes, whence would follow a recefs 
of the waters from thefe parts of the world to thofe, 
and an appearance of many parts above the furfaceof 
the water in the form of IflandSj, and of other places 
formerly above the Sea now in the form of Moun- 
tains, fo to continue till by the libration or other- 
ways returning motion thereof it jrepoffefs its former 
feat and place, and overwhelms again all thofe places 
which in the kiterim had been dry and uncovered with 
the return of the fame water 3 fince nothing in nature 
is found exempt from the ftate of change and cor- 



Farther- 



II w 

Further, it is probable that Earthquakes may have 
been much more frequent in former Ages than they 
have been in thefe latter, the confideration of which 
willpoffibly make this Aflfertion not fo Paradoxical as 
at firft bearing it may feem to be 3 though even thefe 
latter Ages have not been wholly barren of Inftances 
of the being and effects of them, to convince you of 
which I have hereunto fubjoyned a Relation and ac- 
count of one very newly which hapned in the Ifle of 
Palma among the Canaries. 

Next, the clearnefs of the Air is very remarka- 
ble, which made an Ifland which lay eight Leagues 
off to look as if it wereclofe by. To this purpofe 
I have often taken notice of the great difference there 
is between the Air very near the lower Surface of the 
Earth, and that which is at a good diftance from it 5 
That which is very near thp earth being generally fo 
thick and opacous that bodies cannot at any conftdera- 
ble diftance be feen diftinctly through it: But the far- 
ther the eye and object are elevated above this thick 
Air, the more clear do the objects appear. And I 
have divers times taken notice that the fame object 
feen from the top and bottom of a highToWer hath 
appeared twice as far off when feen at the bottom as 
when feen at the top: For the Eye doth very much 
judge of the diftance of Objects according as the 
Denfity of the Air between the Eye and Object doth 
reprefent them. Hence I have feen men look of Gi- 
gantick bignefs in a fog, eaufed by reafbn that the 
Fog made the Eye judge the Object much farther off 
than really it was, when at the fame time the vifible 
Angle altered not. . This great thicknefs of the lower 
Air is fufficiently manifeft in the Coeleftial bodies, few 
of the fixt Stars or fmaller Planets being vifible 
till they are a confiderable way raifed above the Ho- 
rizon. 

The third remark about the moiftnefs of the fogs, 
aad the production of water at that height I have be- 
ll 2 fore 



[SO 

fore infilled on. Only the almoft continual fogs that 
this Gentleman 1 obferved in the Wood they palled is 
very remarkable for the origine of Springs. 

Nor (hall I fay any thing concerning the vaft per- 
pendicular height of the fame 9 but for a clofe of this 
prefentcolle&ionllhalladd the fhort account of the 
Eruption which lately hapned in the Palma, 



J true Relation of the Vulcanos iphich broke mt m 
the IJland of the Palma NoVemb. 13.1 6yj. 

SAturday the thirteenth of November 1677. a quar- 
ter of an hour after Sun fet hapned a (haking or 
Earthquake in the Ifland of St. Michael de la Palma^ 
one of the Canary Iflands, from the lower Pyrentia 7 
and within a League of the City unto the Port of 
Tajjacorte^ which is accounted thirteen Leagues diftant 
along the Goa(r, but more efpecially at or about a 
place called Fuencalient^ being feven Leagues from 
the Town to the Southwards. The trembling of the 
earth was' obferved to be more frequent and violent 
than elfewhere, and fo it continued till Wednefday 
the 1 7. ditto. The People thereabouts were much 
affrighted, for befides the Earthquake there was often 
heard a thundring noife as in the bowels of the earth 
cm a Plain called thtCanios^ which is before you come 
to the great defcent towards the Sea, where the hot 
Baths ftand,- or the holy Fountain $ likewife af the 
afcent from the aforefaid Plain upwards at the great 
and wearifom Hill,called Cmjia Canfada^n& until the 
Mountain ofGoatyards, and the fame day in and about 
the faid places mentioned, the Earth began to open 
feveral mouths, the greateft of them upon the faid 
Goat Mountain^ being diftant from the Sea a mile and 
ariha : lf 3 and from the faid opening came forth a very 

great < 



1.5?] 

great heat and fmell of Brimftone 5 and the fame day,an ' 
hour before Sun-fet at one of the mouths of the wea- 
rifom Hill was a trembling thereabout with more vio- 
lence than any of the four days before} and a great and 
black fmoak came forth with a terrible thundring noiie, 
opening a very wide mouth, and throwing out much 
fire, with melted Rocks and ftones 5 and immediately 
after at another place eighty paces below hapned the 
like terrible noife and fight, and in lefs than a quarter 
of an hour after there opened to the quantity of eigh- 
teen mouths towards the foot of the faid Mountains 5 
and there iflued out fi re, melted Rocks,and other bitu- 
minous matter from all the faid mouths, and was pre- 
fently formed into a great River of fire,which took its 
courfe over the firft mentioned Plain, flowly going 
down towards the faid holy Fountain 5 but it pleafed 
God, being come within eight (paces of the Brink of 
the faid great defcent, it turned a little on the right 
fide, and took its courfe with a very great fall to- 
wards the old Port, which is that which, was firft 
entred by the* Spaniards when, they took the 
Iflands. 

Friday the nineteenth at two a clock in the after- 
noon in the aforefaid Mountain of Goats,on the other 
fide of Taffacorte, there opened another mouth 
with much fmoak and ftones of fire, and fo clofed 
again. But the next day ( the twentieth ) it began:, 
again to fmoak, and continued with great trem- 
bling and noife in the bowels^of the Earth until 
Sunday the twenty firft at noon, when with many 
flafhings of fir e, and a greater thundring noife it 
finifhed that opening of that monftrous birth, call- 
ing up into the Air both fire and ftones, and at night 
the fmoak ceafing, the thundring noife, fire and ftones * 
increafed, forcing great fiery ftones fo high into the 
Air as we loft fight of them, and with fuch violence 
fent them upwards that according tothebeft judg- 
ment they were five times longer, ia falling down, , 

H. s which.. 



[54] 
which ftones or Rocks were obferved to be bigger 

than a Hogfhead, 3 and what was mod to be admired 
was, that thefe breaking in the Air, and changing into 
many feveral fliapes, diftin&ly appearing, yet not- 
withftanding did reunite again in falling down. 

Mnnday the twenty fecond it began again to caft 
forth black fmoak for two hours time, and after to 
thunder,and throw up fire and ftones with great vio- 
lence. Tuefday the twenty third at noon it finoa- 
ked again, and from thence until night there was terri- 
ble thundring noife, and calling up of fire and ftones 
more fierce than before 3 and about nine of the clock 
at night a very great trembling of the earth was felt, 
and prefently after followed three great ftones of fire 
in the form of Globes which were forced about half a 
League in height, and then like Granadoes broke in 
the Air with very great noife. Wednefday the twenty 
fourth it was for an hours time very quiet, and 
after it began with greater force than ever before, 
by reafon that fome of the lower and firft mouths 
were partly ftopt, with which the ^forefaid River 
of fire ceafed from running, after it had dammed up 
the Bay of the old Port, with burnt and melted 
Rocks and Stones, and other matter wherewith the 
iaid River had run, and had forced the Sea back- 
ward above a Mufquet (hot at random,andnear twice 
as much in breadth. It ran into the Sea above fixty 
paces. What fell into the Sea went congealing with 
a great fmoak, what came after, forced and ran 
over that which went before, fo that the fmoak was 
very great many paces within the Sea, as far as feven 
fathoms depth, which caufed many men to imagine 
that fome fiich like Vulcano had opened under the 
Sea in the (aid feven fathoms depth. This night it. 
caft up fome ftones like great fiery Globes as the 
former. 

Thursday the twenty fifth it proved yet more 
violent than ever with thundring noife and flafhesof 

fire. 



fire. Friday the twenty fixth, the mouth that was 
at the foot of the Mountain began again to caft up as 
much fire and (tones as ever, and formed two other 
River s^the one taking its courfe to Leeward of the fir ft 
River leading toward the Rocks called de losTacofos 5 
and the other took its way to windward of the firft, di* 
redly towards the Bathes or Holy Fountain 5 and in 
this entrance the mouth of the Monntain was obftr- 
ved to be more quiet , though it caft up much allies 
like black fmall fand. What dammage appears to 
have been done from its beginning to this day the 
twenty fixth of "November ',• being of thirteen days con- 
tinuance, hath been about nine or ten Country 
Houfes burnt, befides Out-houfes, and great Cifterns 
for water, which are the poor Peoples only Remedy 
in thofe parts, and upwards of three hundred Acres 
of ground are quite fpoiled, being covered with 
Rocks, Stones, and other Rubbifti and Sand 5 and 
if, (which God defend J the faid Vulcano do longer 
continue, the damage muft be far greater, efpeei'ally 
if any other mouth fhould break out higher, as it is 
much feared, by reafon the earth in fome places doth 
open with appearances as at firft, fo that all about that 
circuit of the FuencallienteWiW be loft 5 and for what 
already hapned, and yet continues with much terrour, 
befides the fears of more in other parts thereabout, 
the Inhabitants do leave their Habitations, and like 
poor diftrefled people feek relief at the City, and 
many leave the Ifland to feek their fortunes in the 
others. 

From the twenty fixthof November^ that the afore- 
faid Relation was fent for Tenerijf by the Chamber of 
this Jflaiid unto the General, the faid Vulcano con- 
tinued fierce and without ceafing, rather more 
than left, with a terrible thundring noife, calling up 
Fire, Stones, Rocks, and black Afties, and the three 
Rivers of Fire ftill running into the Sea, and hath 
now dammed up all the Baths and holy Fountain^ to 

the 



the great detriment of the Ifland, that yearly recei- 
ved a great benefit thereby, befides many damages 
dayly added to the former. Several other mouths 
have Once opened in the like dreadful manner near 
about the fame place, we fee the great fmoak by 
day, and hear the thunder and noife, like the (hoot- 
ing offof many Cannons, and by night fee alio much 
of the fire very high in the Air fronTthis City, which 
is one and twenty miles from it. 

We are now at the eleventh of December ^ and fear 
we fhall have more to write to you by the next. 

Other Letters of the thirtieth of 'December mention, 
that it then contined much at one as before 5 and fince 
others of the nineteenth of January (ay, it is yet as 
dreadful as ever, aud little likelihood of ceafing • 
from the thirteenth of November that it began to the 
nineteenth of January is about ten Weeks that it hath 
burnt 5 and the laft Letters mention abundance of 
Aflhes or black Sand forced into the Air, and carried 
all over the Jfland, falling thick like Rain, and fre- 
quently gathered in the City, in the Streets, Hou(es 3 
and Gardens, though feven Leagues off. 



FINIS. 



— , — , . — 



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caft fide. F&Af.iQtVnncht.Vuncis* 



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